Fuse - class-XII
Description: fuse | |
Number of Questions: 82 | |
Created by: Girish Goud | |
Tags: electric circuits effects of electric current electric current and its effects electrical appliances in everyday life when current flows electric charge and electric current effect of electric current physics electricity electric current, potential difference and resistance |
Three fuse wires A, B and C tinned copper having identical cross section and length 8 cm, 12 cm and 16 cm are used as fuses. For the same value of current
-
fuse A will melt first
-
fuse B will melt first
-
fuse C will melt first
-
all fuse will melt for same current
Heat lost per second per unit surface area of fuse wire is
$H = \dfrac{I^2 \rho }{2 \pi ^2 r^3}$
$\Rightarrow I^2 \propto r^3$
$\Rightarrow I \propto r^{\dfrac{3}{2}}$
Hence, all fuse will melt for same current as they are independent of length of fuse wire.
The specific resistance of fuse wire is
-
high
-
low
-
zero
-
infinity
Answer: B
a fuse wire is a type of high resistance resistor that acts as a sacrificial device to provide over current protection, of either the load or source circuit. resistivity is directly depend on resistance for a particular conductor , hence high resistance means high resistivity which is called specific resistance.
What is the meaning of the statement "the current rating of a fuse is $5 A$" ?
-
Maximum $10 A$ pass through it after it will melt.
-
Maximum $5 A$ pass through it after it will melt.
-
Maximum $2 A$ pass through it after it will melt.
-
Maximum $1 A$ pass through it after it will melt.
Fuses are safety devices that are to be built into our electrical system. If there were no fuses and we operated too many appliances on a single circuit, the cable carrying the power for that circuit would get extremely hot, short circuit, and possibly start a fire. To prevent electrical overloads, fuses are designed to trip or blow, stopping the flow of current to the overloaded cable.
Fuse is a piece of wire of a material with a very low melting point. When a high current flows through the circuit due to overloading or short circuit, the wires gets heated and melts. As a result, the circuit is broken and current stops flowing.
The fuse must always be connected to the mains and it must be of correct current rating. For example, a 15-ampere fuse should trip when the current through it exceeds 15 amperes. A 20-ampere fuse should blow when the current through it exceeds 20 amps.
Hence, the statement 'the current rating of a fuse is 5 A' means that the fuse should trip when the current through it exceeds 5 amperes. So correct option is B.
Complete the following sentences :
-
series, neutal
-
series, earth
-
series, live
-
parallel, live
In our homes, we receive supply of electric power through a main supply (mains), either supported through overhead electric poles or by underground cables.The live wire and neutral wire, coming from the electric pole, enter a box fitted just outside our house which has a main fuse. The fuse is connected in series with the live wire. This is done so because it is only the live wire which has a high potential of 220 volts unlike the neutral wire which carries zero potential. The fuse has a high rating of about 50 amperes. Thus it prevents any damage such as fire to the entire electrical wiring entering the house due to short-circuit or overloading.
The two wires then enter the electricity meter which records the electrical power consumed by us in kilowatt-hour (kWh).
Hence, A fuse is connected in series with the live wire.
Which is / are the material used for making the fuse wire.
-
Copper
-
Glass
-
Silver
-
Silicon
A fuse consists of a metal strip or wire fuse element, of small cross-section compared to the circuit conductors, mounted between a pair of electrical terminals, and (usually) enclosed by a non-combustible housing. The fuse is arranged in series to carry all the current passing through the protected circuit. The resistance of the element generates heat due to the current flow. The size and construction of the element is (empirically) determined so that the heat produced for a normal current does not cause the element to attain a high temperature. If too high a current flows, the element rises to a higher temperature and either directly melts, or else melts a soldered joint within the fuse, opening the circuit.
The fuse element is made of zinc, copper, silver, aluminum, or alloys of tin and lead to provide stable and predictable characteristics. The fuse ideally would carry its rated current indefinitely, and melt quickly on a small excess. The element must not be damaged by minor harmless surges of current, and must not oxidize or change its behavior after possibly years of service.
The main fuse is connected in :
-
live wire.
-
neutral wire.
-
both the live and earth wires.
-
both earth and neutral wire.
The live wires coming out from the output terminals of kWh meter has another fuse in it called the main fuse.
The fuse is connected in series with the live wire before it enters the household circuit. This is done so because it is only the live wire which has a high potential of 220 volts unlike the neutral wire which carries zero potential. The fuse has a high rating of about 50 amperes. Thus it prevents any damage such as fire to the entire electrical wiring entering the house due to short-circuit or overloading.Hence correct option is A.
Where the main fuse in a house circuit is connected ?
-
In live wire before the ring system.
-
In ground wire.
-
In neutral wire.
-
In between ground and live.
The live wires coming out from the output terminals of kWh meter has another fuse in it called the main fuse.
The fuse is connected in series with the live wire before it enters the household circuit. This is done so because it is only the live wire which has a high potential of 220 volts unlike the neutral wire which carries zero potential. The fuse has a high rating of about 50 amperes. Thus it prevents any damage such as fire to the entire electrical wiring entering the house due to short-circuit or overloading.Hence correct option is A.
Why is the fuse wire fitted in a porcelain casing ?
-
Porcelian is an insulator of electricity
-
Porcelian is a conductor of electricity
-
Porcelian is a semiconductor of electricity
-
None of these.
The fuse consists of a porcelain base on which two metal contacts are fixed. The incoming and outgoing phase wires are connected to these metal contacts. Porcelain made fuse carrier used for holding the fuse element or fuse wire. This porcelain made fuse carrier is inserted to the porcelain base for connecting a load side circuit to source side circuit. The main advantage of this type of fuse is that, the fuse carrier can be removed from the fuse base without any chance of coming in contact with the live part of the circuit.
What should be the characteristic of fuse wire?
-
High melting point, high specific resistance
-
Low melting point, low specific resistance
-
High melting point, low specific resistance
-
Low melting point, high specific resistance
Fuse wire are used in electric circuits to protect home appliances from damaging by huge amount amount of current. Fuse wire should be such that it melts immediately when strong current flows through the circuit. The same is possible if its melting point is low and resistivity or the resistance is high.
Two identical fuses are rated at 10 A. If they are joined
(A) in parallel, the combination acts as a fuse of rating 20 A
(B) in parallel, the combination acts as a fuse of rating 5 A
(C) in series, the combination acts as a fuse of rating 10 A
(D) in series, the combination acts as a fuse of rating 20 A
Select the correct options
-
A, B
-
A, C
-
B, D
-
B, C, D
The rating of fuse is ,if the current is greater than the rated current then the fuse blows.
So if the rating is 10A, then it is the maximum current that passes through fuse.
If two such fuses are connected in parallel , the total current divides into two components where each can be maximum of 10 A. The maximum total current can be 20 A.
If they are connected in series,same current flows through each of them. The maximum current allowed would be the minimum rated current among the two fuses.So here the current rating will be 10A.
The cable of an electric fan becomes so worn that the live wire makes electrical contact with the metal case The case is earthed The plug to the fan contains a 5 A fuse There is a current of 4 A when the fan works normally What will happen in this case?
-
The current will run to earth and the fuse will not be affected
-
The metal case will become very hot
-
The metal case will become live and dangerous
-
The fuse will melt and switch off the circuit
Answer is D.
When the live wire (high potential) is in contact with the earthed metal case (zero potential) and since there is a potential difference, current flows. As there is little to no resistance in the completed path, the current flow is very large (larger than 4 A melting the fuse). The fuse melts due to high current surge and switches off the circuit.
On Diwali Mr.Antriksh wants to light his house with a number of $10 W (220 V)$ bulbs in parallel. If the house circuit has a fuse of $5 A$ then what is the maximum number of such bulbs he can use if he is not using any other electrical appliance in the circuit.
-
$10$
-
$11$
-
$100$
-
$110$
Answer is D.
The power dissipated is given as P=VI.
In this case, the power of each the bulb is 10 W which uses 220 V supply.
So, the amount of current used is I=P/V = 10/220 = 0.045 A.
The fuse has a power rating of 5 A. Hence, 5 A / 0.045 A = 111 such bulbs can be connected in parallel with security.
Hence, Mr. Antriksh can use 110 bulbs without any problem.
The function of a fuse wire is independent of :
-
its specific resistance
-
its radius
-
its length
-
current flowing through it
Answer is C.
A fuse consists of a metal strip or wire fuse element, of small cross-section compared to the circuit conductors, mounted between a pair of electrical terminals, and (usually) enclosed by a non-combustible housing. The fuse is arranged in series to carry all the current passing through the protected circuit. The resistance of the element generates heat due to the current flow. The size and construction of the element is (empirically) determined so that the heat produced for a normal current does not cause the element to attain a high temperature. If too high a current flows, the element rises to a higher temperature and either directly melts, or else melts a soldered joint within the fuse, opening the circuit and the current stops flowing through it.
Hence, the length of the fuse wire is does not matter.
The material used for a fuse wire should have
-
Low melting point
-
High melting point
-
High electrode potential
-
High resistivity
The material used for a fuse wire must have a low melting point so that it melts as soon as excessive current passes through it and thus it can prevent the appliance from damage.
A car headlamp of 48 W works on the car battery of 12 V. The correct fuse for the circuit is
-
5A
-
2A
-
3A
-
15A
Answer is A.
Fuses are safety devices that are to be built into our electrical system. If there were no fuses and we operated too many appliances on a single circuit, the cable carrying the power for that circuit would get extremely hot, short circuit, and possibly start a fire. To prevent electrical overloads, fuses are designed to trip or blow, stopping the flow of current to the overloaded cable.
The fuse must always be connected to the mains and it must be of correct value. For example, a 15-ampere fuse should trip when the current through it exceeds 15 amperes. A 20-ampere fuse should blow when the current through it exceeds 20 amps.
In this case, the car headlamp is 48 W and the voltage is 12 V.
That is, P = VI, I = P/V = 48/12 = 4 A.
Hence, the fuse of 5 A should be connected to the circuit.
The circuit breaker device which can be used in place of a fuse is called
-
CBD
-
MCB
-
MCD
-
CBF
Answer is B.
Fuse boxes contain safety devices called fuses or circuit breakers - MCB (Miniature Circuit Breaker) which are designed to prevent an excess of electric current entering your house by only allowing a certain maximum current to flow in. When the electrical current is too large, an electromagnet attracts a spring loaded switch which breaks the circuit and cuts the power supply. The switch must be reset before any current can flow again.
In an electric circuit, a fuse is connected :
-
in the live wire
-
in the neutral wire
-
in the earth wire
-
Any of these
Answer is A.
The live wire and neutral wire, coming from the electric pole, enter a box fitted just outside our house which has a main fuse F1. The fuse is connected in series with the live wire. This is done so because it is only the live wire which has a high potential of 220 volts unlike the neutral wire which carries zero potential.
What is immaterial for an electric fuse?
-
Its length
-
Its radius
-
Its specific resistance
-
Current flowing through it
Its length is immaterial for an electric fuse fuse is used to avoid danger due to high current if high current is passed through the fuse it burns and disconnect the power supply the thickness of fuse determines how much current can be pass hence fuse of any length can be used but it's thickness should be proper
Fuses are connected in ________ to the live wire:
-
parallel
-
series
-
either way
-
None
Answer is B.
The live wire and neutral wire, coming from the electric pole, enter a box fitted just outside our house which has a main fuse F1. The fuse is connected in series with the live wire. This is done so because it is only the live wire which has a high potential of 220 volts unlike the neutral wire which carries zero potential.
The essential requirements of a fuse wire are ___________.
-
High resistance and high melting point
-
High resistance and low melting point
-
Low resistance and low melting point
-
Low resistance and high melting point
The fuse wire is made of zinc, copper, silver, aluminum, or alloys to provide stable and predictable characteristics. Fuse should be of low resistance and low melting point as per the requirement current rating for overcurrent protection.
Fuse wire is a
-
tin-lead alloy
-
copper-lead alloy
-
tin-copper alloy
-
silver-lead alloy
-
True
-
False
A fuse is always connected to the neutral wire.T his statement is false. Fuse is connected to live wire.
Fuse is always connected to the ______ wire.
-
live
-
neutral
-
earth
-
green
Fuse is always connected to live wire. The purpose of a fuse is to protect the wiring and equipment from overloading
-
True
-
False
Yes,given statement is true, because short-cicuiting is an excessive current flow in the power source through the short due to which the fuse wire melts and breaks the electric circuit.
A fuse is connected to the
-
Live wire
-
Neutral wire
-
Earth wire
-
None of these
Fuses are always connected in series with the components to be protected from overcurrent, so that when the fuse blows (opens) it will open the entire circuit and stop current through the components. A fuse connected in one branch of a parallel circuit, of course, would not affect current through any of the other branches.
-
True
-
False
Fuses should be connected to the neutral wire.T his statement is false fuses should be connected to live wire.
Fuses used in a household generally have a rating of:
-
500A
-
5A
-
30A
-
220A
Fuses used in household generally have a rating of 5A to prevent fuse to melt and prevent circuit to break.
If a fuse is rated as 8 A, and current more than 8 A passes through it then
-
it would melt
-
circuit gets broken
-
both
-
none
The maximum current which can flow through a fuse without melting it is called its rating.for example a fuse rated at 8A,can stand current upto 8 A. If current higher than 8 A flows through the fuse, it would melt and circuit gets broken the rating of a fuse depends upon the thickness of the fuse wire (because length of the wire is fixed). The thicker fuse has higher rating. So, the thickness of the fuse wire in 8 A circuit is more than that of the fuse wire in 5 A circuit.
Material used in fuse wire must have
-
high melting point
-
low melting point
-
high resistance
-
none
A fuse is a piece of thin wire of a material having low melting point, high resistance. It is based in heating effect on current.
Fuse wire is made up of
-
Alloy
-
Mixture
-
Metals
-
Non metals
Fuse is generally made up of an alloy of tin and lead. It is used in series with an appliance to prevent it from damage when excessive flows through the appliance. Material to be used in fuse wire must have Low melting point, low boiling point and high electric resistance.
Mark the correct statement about the material to be used in fuse wire.
-
Low melting point
-
Low boiling point
-
High electric resistance
-
All
Fuse wire has
Mark the correct reason why a fuse is always connected in series
-
When fuse melts, it breaks down the entire home circuit and no current flows
-
In series connection the current for the entire house pass through the fuse
-
Both
-
None
A fuse is always connected in series because
Which of the following is the function of MCB in household circuit?
-
This switches automatically turn off when current exceeds safe limit
-
This switches automatically turn on when current exceeds safe limit
-
Saves the electrical appliances from getting damaged due to excess current
-
Saves from shortcircuiting
An MCB functions by interrupting the continuity of electrical flow through the circuit once a fault is detected. In simple terms MCB is a switch which automatically turns off when the current flowing through it passes the maximum allowable limit.
What is MCB in household circuit connection?
-
Micro Circuit Breakers
-
Miniature Circuit Breakers
-
Miniature Circuit Builders
-
Mega Circuit Blockers
An MCB or miniature circuit breaker is an electromagnetic device that embodies complete enclosure in a molded insulating material.
What is/are the advantage of MCB over fuses?
-
Its wire melts unlike fuses wire
-
It automatically turn off to save from excess electricity
-
It takes less time to break the circuit as compare to fuse while overloading
-
None of these
- MCB is more sensitive to current than the fuse. It detects any abnormality in the current flow and automatically switches off the electrical circuit.
- In the case of MCB, the fault zone of the electrical circuit can be easily identified. Faulty circuit trips to the off position. On the other hand in case of the fuse, the complete fuse wire needs to be checked by opening fuse grip for confirming the fault zone.
- With MCB it is very simple to resume to the supply. You just need to push the knob of MCB back to on position. But in case of the fuse, the entire fuse wire needs to be replaced.
- MCB provides a better interface with the help of knob than a fuse. In case of the fuse, the compete for handle needs to be taken care out.
- Handling MCB is electrically safer than handling a fuse.
- MCB is reusable and hence has less maintenance and replacement cost. Whereas a fuse needs to be replaced whenever it goes faulty.
Choose the correct option
-
MCB is much more sensitive to over current than fuse
-
Fuse is much more sensitive to over current than MCB
-
Handling MCB is more electrically safe than fuse
-
Handling fuse is more electrically safe than MCB
Nowadays MCB in low voltage electrical network is commonly used instead of fuse. The fuse may not sense the overcurrent but the miniature circuit breaker does it in a more reliable way. MCB is much more sensitive to over current than fuse. Handling a MCB is electrically safer than a fuse.
In electric fuse, some special wire is used, which is having _______ melting point
-
low
-
high
-
moderate
-
very high
Fuse is a piece of a wire of material with a very low melting point. When a high current flows through the circuit due to overloading or short circuit, the wire gets heated up and melts.
Electric fuses is a _____________ to electrical circuits.
-
safety device which prevents damages
-
device which causes damage and fire
-
simple device which pass current
-
None of these
A fuse is an electrical safety device (a component) that removes electrical current from an electrical circuit when the current in the electrical circuit is too high.
Which wire could be used as a fuse wire?
-
Nichrome wire
-
Zinc
-
Copper
-
Silver
The fuse element is made of zinc, copper, silver, aluminum, or alloys to provide stable and predictable characteristics. The fuse ideally would carry its rated current indefinitely, and melt quickly on a small excess.
Fuse wire is a wire of
-
high resistance and high melting point
-
high resistance and low melting point
-
low resistance and low melting point
-
low resistance and high melting point
A fuse is a short piece of wire of .............. and ................?
-
high resistance, low melting point
-
high resistance, high melting point
-
low resistance, low melting point
-
low resistance, high melting point
A fuse wire has a HIGH resistance & LESS melting point. so that it can protect the electric appliances at home by undergoing melting due to excess heat produced because of high resistance.
Fuse has ..... and .....?
-
high resistance, high melting point
-
high resistance, low melting point
-
low resistance, high melting point
-
low resistance, low melting point
Melting point of a fuse wire is low. So by any chance if high current flows through the circuit, the fuse melts because of heat produced in the circuit beyond a permissible limit. A fuse must have high resistance so as to oppose the current flowing through it beyond a safe limit.
two identical fuses are rated at 10 A , if they are joined
-
in parallel, the combination acts as a fuse of rating 20 A
-
in parallel, the combination acts as a fuse of rating 5 A
-
in series , the combination acts as a fuse of rating 10 A
-
in series, the combination acts as a fuse of rating 20 A
Two identical fuses are rated at $10\space A$. If they are joined
-
in parallel, the combination acts as a fuse of rating $20\space A$
-
in parallel, the combination acts as a fuse of rating $5\space A$
-
in series, the combination acts as a fuse of rating $10\space A$
-
in series, the combination acts as a fuse of rating $20\space A$
A fuse is a type of low resistance resistor that acts as a device to provide over-current protection, of either the load or source circuit.
Where several fuses are connected in series, it is desirable to blow (clear) only the fuse (or other over-current device) electrically closest to the fault. Hence, when two fuses are in series the current rating is simply the current rating of each fuse i.e. in series, the combination acts as a fuse of rating 10 A
When two fuses are in parallel the current rating is simply twice the current rating of each fuse, hence, in parallel, the combination acts as a fuse of rating 20 A.
What is immaterial for an electric fuse wire ?
-
Its specific resistance
-
Its radius
-
Its length
-
Current flowing through it
Name the material used for fuse wire :
-
Electric fuse.
-
Connecting wire.
-
Filament of an electric bulb.
-
Heating element of an electric toaster.
What is immaterial for an electric fuse wire
-
Specific resistance of the wire
-
radius of the wire
-
length of the wire
-
current flowing through the wire
An electric bulb rated 220 V - 100 W will fuse if it consumes 131 W. What voltage fluctuations can it withstand?
-
up to 230 V
-
up to 241 V
-
up to 225 V
-
up to 252 V
We know that: $P = \dfrac{V^{2}}{R}$
Using the fact that the bulb is $220V - 100W$
$ 100 = \dfrac{220^{2}}{R}$
Substituting this:
$131 = \dfrac{V^{2}}{484}$
An 1800 W toaster, a 1.3 kW frying pan are plugged into the same $20 A-120V$ line then
-
fuse will not blow
-
fuse will blow
-
supply will spark
-
fuse is just saved
$I _{toaster}=\dfrac{1800}{120}= 15 A,$
$I _{frying pan}=\dfrac{1300}{120}= 10.83 A$
$I _{net}= 25.83 A > 20 A$
A fuse wire of radius $0.2$ mm blows out for a current of $5A$. For what current, another fuse wire of same material but of radius $0.3$ mm will blow out?
-
$5$A
-
$3.2$A
-
$4.33$A
-
$11.2$A
A fuse wire of circular cross-section and having diameter of $0.4$ mm, allows $3$A of current to pass through it. But if another fuse wire of same material and circular cross-section and having diameter of $0.6$ mm is taken, then the amount of current passed through the fuse is?
-
$3$A
-
$3\times \sqrt{\dfrac{3}{2}}$A
-
$3\times\left(\dfrac{3}{2}\right)^{3/2}$A
-
$3\times \left(\dfrac{3}{2}\right)$A
what is a fuse ?
-
Over current protection
-
low resistance and high melting point wire.
-
low resistance and low melting point wire.
-
high resistance and low melting point wire.
Fuses are safety devices that are to be built into our electrical system. If there were no fuses and we operated too many appliances on a single circuit, the cable carrying the power for that circuit would get extremely hot, short circuit, and possibly start a fire. To prevent electrical overloads, fuses are designed to trip or blow, stopping the flow of current to the overloaded cable.
Fuse is a piece of wire of a material with a very low melting point. When a high current flows through the circuit due to overloading or short circuit, the wires gets heated and melts. As a result, the circuit is broken and current stops flowing.
Hence, the fuse element is made of zinc, copper, silver, aluminum, or alloys to provide stable and predictable characteristics.
The fuse must always be connected to the mains and it must be of correct value. For example, a 15-ampere fuse should trip when the current through it exceeds 15 amperes. A 20-ampere fuse should blow when the current through it exceeds 20 amps.
What we used to protect the electric circuits from over loading and short circuit ?
-
capacitance
-
inductance
-
fuse wire
-
filament wire.
A fuse is the device to protect the electric circuits from over loading and short circuit.
Fuses are safety devices that are to be built into our electrical system. If there were no fuses and we operated too many appliances on a single circuit, the cable carrying the power for that circuit would get extremely hot, short circuit, and possibly start a fire. To prevent electrical overloads, fuses are designed to trip or blow, stopping the flow of current to the overloaded cable.
Fuse is a piece of wire of a material with a very low melting point. When a high current flows through the circuit due to overloading or short circuit, the wires gets heated and melts. As a result, the circuit is broken and current stops flowing.
Hence, the fuse element is made of zinc, copper, silver, aluminum, or alloys to provide stable and predictable characteristics.
The fuse must always be connected to the mains and it must be of correct value. For example, a 15-ampere fuse should trip when the current through it exceeds 15 amperes. A 20-ampere fuse should blow when the current through it exceeds 20 amps. Hence correct option is C.
Complete the following sentences :
-
resistance, melting point
-
meting point, resistance
-
capacitance, melting point.
-
conductance, melting point
A fuse is the device to protect the electric circuits from over loading and short circuit.
Fuses are safety devices that are to be built into our electrical system. If there were no fuses and we operated too many appliances on a single circuit, the cable carrying the power for that circuit would get extremely hot, short circuit, and possibly start a fire. To prevent electrical overloads, fuses are designed to trip or blow, stopping the flow of current to the overloaded cable.
Fuse is a piece of wire of a material with a very low melting point. When a high current flows through the circuit due to overloading or short circuit, the wires gets heated and melts. As a result, the circuit is broken and current stops flowing.
Hence, the fuse element is made of zinc, copper, silver, aluminum, or alloys to provide stable and predictable characteristics.
The fuse must always be connected to the mains and it must be of correct value. For example, a 15-ampere fuse should trip when the current through it exceeds 15 amperes. A 20-ampere fuse should blow when the current through it exceeds 20 amps.
Hence, A fuse is a short piece of wire of high resistance and of material of low melting point.
Complete the following sentences :
-
lead, tin
-
nickel , lead
-
cadmium, lead
-
nickel, tin
A fuse is the device to protect the electric circuits from over loading and short circuit.
Fuses are safety devices that are to be built into our electrical system. If there were no fuses and we operated too many appliances on a single circuit, the cable carrying the power for that circuit would get extremely hot, short circuit, and possibly start a fire. To prevent electrical overloads, fuses are designed to trip or blow, stopping the flow of current to the overloaded cable.
Fuse is a piece of wire of a material with a very low melting point. When a high current flows through the circuit due to overloading or short circuit, the wires gets heated and melts. As a result, the circuit is broken and current stops flowing.
Hence, the fuse element is made of zinc, copper, silver, aluminum, or alloys to provide stable and predictable characteristics.
The fuse must always be connected to the mains and it must be of correct value. For example, a 15-ampere fuse should trip when the current through it exceeds 15 amperes. A 20-ampere fuse should blow when the current through it exceeds 20 amps.
Hence, A fuse wire is made of an alloy of lead and tin If the current in a circuit rises too high, the fuse wire melts.
The rating of a fuse connected in the general household lighting circuit is:
-
15 A
-
5 A
-
10 A
-
zero
General household wire has a current supply of 5 ampere. Hence fuse also have that. hence The rating of a fuse connected in the general household lighting circuit is $5A$
What is the current through an electrical appliance of rating 5 kW, 200 V and can you use a fuse which is rated 8 A ?
-
25 A, yes
-
2.5 A, yes
-
25 A, no
-
2.5 A, no
Fuses are safety devices that are to be built into our electrical system. If there were no fuses and we operated too many appliances on a single circuit, the cable carrying the power for that circuit would get extremely hot, short circuit, and possibly start a fire. To prevent electrical overloads, fuses are designed to trip or blow, stopping the flow of current to the overloaded cable.
The fuse must always be connected to the mains and it must be of correct value. For example, a 15-ampere fuse should trip when the current through it exceeds 15 amperes. A 20-ampere fuse should blow when the current through it exceeds 20 amps.
In this case, let us consider a device of power 5 kW, that is, 5000 W and 200 V.
Two fuse wires of same length are rated 5 A and 20 A. Which is the correct ?
-
both wire will be same thickness.
-
20 A wire is more thicker
-
5 A wire more thicker
-
none of these.
The fuse must always be connected to the mains and it must be of correct value. For example, a 15-ampere fuse should trip when the current through it exceeds 15 amperes. A 20-ampere fuse should blow when the current through it exceeds 20 amps.
As we know, the cross-sectional area of the wires will affect the amount of resistance. Wider wires have a greater cross-sectional area. Water will flow through a wider pipe at a higher rate than it will flow through a narrow pipe. This can be attributed to the lower amount of resistance that is present in the wider pipe. In the same manner, the wider the wire, the less resistance that there will be to the flow of electric charge. When all other variables are the same, charge will flow at higher rates that is, more current through wider wires with greater cross-sectional areas than through thinner wires.
Hence, the 20 A wire is the thicker wire as more amount of current flow through it than the 5 A wire.
Which are the correct for fuse wire?
-
High resistance
-
low resistance.
-
low melting point.
-
high melting point.
The electrical resistance of an electrical conductor is the opposition to the passage of an electric current through that conductor. The SI unit of electrical resistance is the ohm $\Omega $.
When the opposition to the passage of an electric current through that conductor is more it is called high resistance and when the opposition to the passage of an electric current through that conductor is less it is called low resistance.
The amount of resistance determines whether the circuit is a good conductor low resistance, or a bad conductor high resistance.
Which one is correct for fuse wire ?
-
low resistance and low melting point
-
high resistance and high melting point
-
high resistance and low melting point
-
low resistance and high melting point
Fuses are safety devices that are to be built into our electrical system. If there were no fuses and we operated too many appliances on a single circuit, the cable carrying the power for that circuit would get extremely hot, short circuit, and possibly start a fire. To prevent electrical overloads, fuses are designed to trip or blow, stopping the flow of current to the overloaded cable.
Fuse is a piece of wire of a material with a very low melting point. When a high current flows through the circuit due to overloading or short circuit, the wires gets heated and melts. As a result, the circuit is broken and current stops flowing.
Hence, the statement is true as the material used for fuse has low melting point.
You are given two fuse wires A and B with current rating 2.5 A and 6 A respectively. Which of the two wires would you select for use with a 1100 W, 220 V room heater?
-
A
-
B
-
A and B
-
None of these
Fuse is a piece of wire of a material with a very low melting point. When a high current flows through the circuit due to overloading or short circuit, the wires gets heated and melts. As a result, the circuit is broken and current stops flowing.
The fuse must always be connected to the mains and it must be of correct value. For example, a 15-ampere fuse should trip when the current through it exceeds 15 amperes. A 20-ampere fuse should blow when the current through it exceeds 20 amps.
In this case, the electrical appliance is of 1100 W power and 220 V. So the current that passes through the appliance is calculated from P=VI. That is, I=P/V.
So, I = 1100 W/220 V = 5 A.
Hence, the wire B with current rating of 6 A should be used for the fuse.
Which one of the following statements is not correct?
-
The two main organs of the human body where the magnetic field produced is quite significant are the heart and the brain.
-
In a house circuit, lamps are used in parallel
-
Switches,fuses and circuit breakers should be placed in the neutral wire
-
A generator with commutator produces direct current
Switches, fuses and circuit breakers must be placed in the live wire, not in neutral wire. And all the other statements given are correct.
The commonly used safety fuse wire is made of
-
copper
-
lead
-
nickel
-
an alloy of tin and lead
The commonly used fuse wire is made of an alloy of tin and lead.
Two identical fuses are rated at 10A. If they are joined
-
in parallel, the combination acts as a fuse of rating 20A
-
in parallel, the combination acts as a fuse of rating 5A
-
in series, the combination acts as a fuse of rating 10A.
-
in series, the combination acts as a fuse of rating 20A.
A fuse is a piece of wire resistance which acts in a way such that if the voltage in a circuit exceeds the rating of the fuse then the fuse wire melts and the circuit becomes an open circuit, thereby breaking the circuit and preventing the components from getting damaged due to short circuit. Now, if two fuses are in series, the melting of a single fuse can break the circuit and so in series the rating will be 10A. However, in parallel, even if one fuse is melted, the other fuse still works and so the net rating will be 20A.
The lighting circuit of the house has _______ fuse.
-
15A
-
50A
-
5A
-
500A
Usually, there are two separate circuits in a house, the lighting circuit with a 5A fuse and the house circuit with a 15A fuse.
What is the problem when a multi-plugs adaptor is used to connect many appliances to the same socket?
-
The current drawn from the mains gets higher and overheating may occur.
-
The voltage across the live and neutral wires increases and overheating may occur.
-
The flow of the current will be slowed down and the power to each appliance will be reduced.
-
The appliances will be damaged due to the higher current that flows through each appliance.
- This means much amount of current will be drawn from the socket.
- If we plug in a washing machine,a hair dryer ,a 1 HP mixer grinder then out socket will simply melt.
- So by using multi-plugs adapter current drawn increase result in over heating.
What is the reason for the fuse and switch to be located at the live wire?
-
To cut off the current from the appliance.
-
To cut off the high voltage from the appliance.
-
To break the circuit when there is a sudden current surge.
-
To indicate to the user that the wire is Live wire when fuse and switch is seen on it.
When by short-circuit or any other reason current exceed its nominal value that time fuse breaks the circuit and so cuts off the high voltage from the appliance which prevent it from damage.
Choose the wrong option regarding miniature circuit breaker (MCB)?
-
MCB contains a metal which melts when the current passing through it exceeds a certain value and hence opens the circuit
-
Quick restoration of an MCB is possible just by switching on the operation when a breakdown occurs due to current overload
-
MCB switchess off the circuit automatically when the current passing through it exceeds a certain value
-
None of the above
In MCB, whenever continuous current flows, the bimetallic strips is heated and deflect by bending. This deflection of bimetallic strips releases the mechanical latch. It causes to open the miniature circuit breakers contact and the MCB turns of thereby stopping he current to flow in the circuit. Hence $A$ is the wrong statement.
If the current in a circuit rises too high, the fuse wire will ?
-
melts
-
cold
-
proivides light
-
hot
Fuse wire have high value of resistance so when high magnitude of current flows through it then due to melting point of it it melts by excessive heating. Fuse is used to protect the circuit from any accidental heavy flow of current.
When a fuse is rated 8A, it means :
-
It will not work if current is less than 8A
-
It has a resistance of 8 ohm
-
It will work only if current is 8A
-
It will burn if current exceeds 8A
The work of fuse wire to protect electric appliances if some particular amount of current that should not be passed through is passed accidentally.
Fuse wire is made of :
-
Platinum
-
Copper
-
Aluminium
-
Alloy in tin and lead
Electric fuse wire is a wire which allows only upto a limit of current through it , if a particular amount of value of current is exceeded then it melts down.
A fuse is used in an electrical appliance :
-
To earth the appliance
-
To protect the appliance and its cable
-
To change the efficiency of the applicance
-
To change the current rating of the applicance
Fuse is a device used to save the electric current from overheating due to the sudden increase in the current in the circuit.
It protects the device and the user when the electric current is higher than the normal needed by a circuit, it blows up breaking the circuit.
Hence protecting the circuit from an a power overload.
Which of the following is false about fuse ?
-
A fuse controls the current that flows to the appliance.
-
A fuse increases the resistance in the circuit to minimize the current flow.
-
A fuse allows high current to flow through the circuit without damaging the appliance.
-
A fuse protects the wiring and the appliance in the circuit from overheating.
A fuse is a type of low resistance resistor that acts as a sacrificial device to provide over current protection, of either the load or source circuit. It just controls the amount of current flowing.
It neither increase the resistance of the circuit nor it allows high current. It doesn't allow high current to pass but that doesn't mean, it protect appliances from heating.
In which of the following situations will a fuse possibly melt?
-
The earth wire is broken
-
There is a short circuit in the electrical circuit
-
The fuse is fixed along the neutral wire instead of the live wire
-
The fuse wire is connected to earth wire
A fuse wire may possibly melt when :
(i) the earth wire is broken
(ii) the fuse is fixed along the neutral wire instead of the live wire.
(iii) there is a short circuit in the electrical circuit.
What specifications would you select for the material to make a fuse wire?
-
Greater specific heat, low melting point
-
Greater specific heat, high melting point
-
Less specific heat, high melting point
-
Less specific heat, low melting point
A fuse wire must be made of a material having less specific heat and low melting point. When the current in electric circuit exceeds a safe, limit, the low value of specific heat results in more increase in temperature and the low value of melting point causes it to melt. It thus saves the electrical appliances from getting damaged.
Fuse blows because ........................... .
-
There is a high voltage connected across the circuit
-
There is a high current flowing through the circuit
-
There is a high charge that has passed through the circuit
-
The effective resistance of the circuit is too high
Fuse are used to protect electric appliances at home from large magnitude of current. they are made up of very high resistance. fuse blows up (Melts) due to overheating when the current through it exceeds the rated current.
A fuse wire with a radius of $0.1 mm$ blows up at $5 A$. The radius of another fuse wire made of the same material which will blow up at $40 A$ is _____.
-
$0.8 mm$
-
$0.6 mm$
-
$0.45 mm$
-
$0.4 mm$
When the circuit is switched on, the temperature of the fuse will increase up to a certain value (below the melting point) and then remains constant At this equilibrium stage, the heat lost by the radiation per second balances the heat liberated per second. That is
$(2\pi rI)H=I^2R$
where $H$ is the rate of loss of heat per unit area, $I$ is the current and $R$ the resistance of the fuse wire.
But $\displaystyle R = \frac {\rho l}{\pi r^2}$
$\displaystyle \therefore H(2\pi rl) = \frac {I^2 \rho l}{\pi r^2}$ or $\displaystyle r^3 = \frac {\rho I _2}{2\pi ^{2}H}$
For a given material of the fuse wire, $\rho$ and $H$ are constants.
$r^3 \propto I^2$
If $r _1$ and $r _2$ are the radii of two fuse wires of the same material which blow $u$ at currents $I _1$ and $I _2$,
respectively, then
$\displaystyle \left ( \frac {r _2}{r _1} \right)^3 = \left ( \frac {I _2}{I _1} \right),$ i.e., $\displaystyle r _2 = r _1 \left ( \frac {I _2}{I _1} \right)^{\displaystyle \frac {2}{3}}$
Given: $I _1 = 5A, r _1 = 0.1 mm, I _2 = 40 A$,
$\displaystyle r _2 = 0.1 \left ( \frac {40}{5}\right)^{\displaystyle \frac {2}{3}} = 0.1 (4) = 0.4mm$
......... suggested that the slips should be marked with load lines
-
Samuel Plimsoll
-
Einstein
-
Newton
-
Archimedes
Fuse should be connected to live / phase wire o fthe circuit. If it is connected to neutral wire , the fuse will melt when excess current flows, but the appliance will still be connected to high potential through live wire. Thus, if a person touches the appliance, he receives shock.
Hence, choice is (3)
-
heating
-
magnetic
-
chemical
-
none of these
Electric fuse work on the principal of heating effect of current . fuse wire is a wire of high resistance and low melting point. when very large current will pass through it, heat will be generated which will melt the fuse wire and break the circuit.By using electric fuses in home we can protect the home appliances from damaging by large amount of current.
A fuse wire is generally made of
-
tin
-
tin-lead alloy
-
copper
-
either (a) or (b) above
Fuse wire are used to save the home appliances from damagaing by large currents. so they are made up of such materials which have high resistance and low melting point so that they can melt down when unexpected amount of current is passed through.for this work either tin metal or tin-lead alloy will be appropriate.
An electric iron draws a current of 15 A from a 220 V supply. What is the cost of using iron for 30 min everyday for 15 days if the cost of unit (1 unit $=$ 1 k W hr) is 2 rupees?
-
Rs. 49.5
-
Rs. 60
-
Rs. 40
-
Rs. 10
$I=15 A, V=220 V, t=30 min$
$Energy=P\times t=VIt$
$=220\times 15\times \frac {30}{60}\times 15$
$=3300\times \frac {1}{2}\times 15 W hr$
$=3.3\times kW\times 7.5 hr$
$=24.75 kW hr$
$Cost=24.75\times 2=Rs. 49.50$
The parameter irrelevant for an electric fuse wire is
-
its radius.
-
its specific resistance.
-
current flowing through it.
-
its length.
For fuse wire expression for heat produced is given by eq. is $H = \dfrac{I^2 \rho}{2 \pi ^2r^3}$
Hence, it is independent on length of fuse wire. Thus, the parameter irrelevant for an electric fuse wire is its length.