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Current in electric circuits - class-XII

Description: current in electric circuits
Number of Questions: 58
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Tags: electrical quantities electric current effects of current electric current, potential difference and resistance electricity physics
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how many electrons should pass through a conductor in $1$ second to constitute 1 amp current, it the charge one Eatonton is $1.6\times{10}^{-19}$

  1. $6.25\times{10}^{18}$

  2. $6.9\times{10}^{18}$

  3. $6.5\times{10}^{19}$

  4. $6.25\times{10}^{15}$


Correct Option: A

Four persons are saying that they carry a negative charge of a certain value.which one of these statements given by the persons is incorrect?

  1. I carry $1.90\times10^{-18}$ coulomb

  2. I carry $1.6\times10^{-18}$ coulomb

  3. I carry $1.92\times10^{-18}$ coulomb

  4. I carry $2.4\times10^{-16}$ coulomb


Correct Option: A

What is the order of colour code for the insulation on the (a) live (b) neutral and (c) earth wire?

  1. Brown, Blue and Green.

  2. Blue, green and brown.

  3. Green, blue and brown.

  4. Green,brown and blue.


Correct Option: A
Explanation:

A 3 pin plug consists of three pins (hence the name). Each pin must be correctly connected to the three wires in the electrical cable. Each wire has its own specified color so as it can be easily identified.
The LIVE wire is RED OR BROWN. This is connected to a fuse on the live pin. The electric current uses the live wire as its route in.
The NEUTRAL wire is BLUE OR BLACK. This is the route the electric current takes when it exits an appliance; it is for this reason the neutral wire has a voltage close to zero.
The EARTH wire is GREEN OR  YELLOW and connected to the earth pin. This is used when the appliance has a metal casing to take any current away if the live wire comes in contact with the casing.

Where the switch is connected in a circuit ? 

  1. in the ground wire.

  2. in the live wire

  3. in the neutral wire

  4. in live and neutral both.


Correct Option: B
Explanation:

A switch opens or closes an electrical circuit. If the circuit is open, no electricity flows. If the circuit is closed, electricity flows through the circuit. 
Example:
A light switch is commonly used. When you turn the switch on, the circuit closes and electricity flows through the light. When you turn the switch off, the circuit is opened and the flow of electricity stops, making the light go out. 
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 live wire is connected to the switch because, the live wire carries a voltage of 220 V and the passage of this voltage can be disabled by switching of the circuit.

The device used for producing current is called a _____.

  1. Voltmeter

  2. Ammeter

  3. Galvanometer

  4. Generator


Correct Option: D
Explanation:

In electricity generation A generator is a device which uses mechanical energy to produce electrical energy which flows in form of electric current in circuits. hence Generator can produce current.

Current in a circuit flows:

  1. in direction from high potential to low potential

  2. in direction from low potential to high potential

  3. in direction of flow of electrons

  4. in any direction.


Correct Option: A
Explanation:

Electric current flows from positive electrode of cell to negative electrode of cell, i.e., from high potential to low potential.

The conventional direction of flow of current is

  1. negative terminal to positive terminal of the cell.

  2. positive terminal to negative terminal of the cell.

  3. opposite direction of electrons

  4. in direction of electrons.


Correct Option: B,C
Explanation:

The current in the wire is due to the drifting of electrons inside a wire in a direction opposite to the flow of electrons. During their drifting they collide with their atoms vibrating about their mean position and lose some of kinetic energy to the vibrating atoms. 
The electrons are negatively charged particles and so, the electrons move towards the positively charged terminal from the negatively charged terminal.
Hence, the statement is true as the conventional direction of flow of current is from positive terminal to negative terminal of the cell.

Name the physical quantity of which the unit is ampere: 

  1. Current.

  2. Capacitance

  3. Charge

  4. Voltage


Correct Option: A
Explanation:

An electric current is a flow of electric charge. In electric circuits this charge is often carried by moving electrons in a wire. It can also be carried by ions in an electrolyte, or by both ions and electrons such as in a plasma.
The SI unit for measuring an electric current is the ampere, which is the flow of electric charge across a surface at the rate of one coulomb per second. Electric current is measured using a device called an ammeter.

The unit of current is :

  1. ampere

  2. volt

  3. ohm

  4. coulomb


Correct Option: A
Explanation:

Current is measured in Coulomb/sec or Ampere. 

In an electric circuit, current starts from the-

  1. Positive terminal

  2. Either of the two terminals

  3. Negative terminal

  4. Depends upon the circuit


Correct Option: A
Explanation:

The direction of an electric current is by convention the direction in which a positive charge would move. Thus, thecurrent in the external circuit is directed away from the positive terminal and toward the negative terminal of the battery. Electrons would actually move through the wires in the opposite direction.

The speed at which the current travels in a conductor, is nearly

  1. $3 \times 10^0 ms^{-1}$

  2. $3 \times 10^5 ms^{-1}$

  3. $4 \times 10^6 ms^{-1}$

  4. $3 \times 10^8 ms^{-1}$


Correct Option: D
Explanation:

Current travels in a conductor at a speed approximately equal to speed of light i.e. $3\times 10^8$ $ms^{-1}$.

Which of the following statements is true?

  1. Electricity can be created

  2. Electricity flows in a circuit with gaps

  3. Electricity is the flow of negative charge

  4. All of the above


Correct Option: C
Explanation:

(A) Option:- Electricity can be created. This statement is false because electricity is basically a form of energy that cannot be created nor be destroyed 


(B) Option:- Electricity flows in a circuit with gaps. This statement is false because electricity does not flow in open circuit.


(C) Option:- Electricity is the flow of negative charges.T his statement is true because due to the flow of electrons electricity is generated electrons are negatively charged.

In a cell, electrons move from:

  1. positive electrode to negative electrode.

  2. negative electrode to positive electrode.

  3. both A and B.

  4. electrons do not move and only negative charge moves from one place to another place.


Correct Option: B
Explanation:

In cells, electrons move from negative electrode to positive electrode and an electron has negative charge. So, we can say that negative charge flows from negative electrode to positive electrode. But, by convention flow of charges are measured only through positive charges.When an electron moves from point A to point B,an equal amount of positive charge moves from point B to point A.

So, the direction of charge is from positive electrode to negative electrode. As unlike charges attract each other and like charges repel each other, thus electrons move from negative electrode to positive electrode inside a cell.

Electric current is the flow of

  1. electrons

  2. protons

  3. neutrons

  4. none of these


Correct Option: A
Explanation:

Electric current is defined as the flow of electrons.

In electrolysis:

  1. positive ions move toward the positive electrode and negative ions toward the negative electrode.

  2. positive ions move toward the negative electrode and negative ions toward the positive electrode.

  3. both ions move toward both the electrodes in equal amounts until they are balanced.

  4. none of the above


Correct Option: B
Explanation:

As unlike charges attract each other and like charges repel each other. Thus in electrolysis, positive ions move towards the negative electrode whereas negative ions move toward the positive electrode.Hence option B is correct.

The direction of current is taken as

  1. The opposite to the direction of flow of current.

  2. Opposite to the direction of flow of protons.

  3. Opposite to the direction of flow of electrons.

  4. All


Correct Option: C
Explanation:
Conventionally, the direction of current is taken as the direction of flow of positive charge (protons) and opposite to the direction of flow of negative charge (electrons).
Hence option C is correct.

In a DC circuit when a switch is closed to operate the circuit, the electrons that cause the current:

  1. travel from the negative plate of the battery to the positive plate

  2. travel from the positive plate of the battery to the negative plate

  3. travel from one resistance to the next resistance

  4. travel from the negative plate of the battery to the positive plate inside the battery

  5. travel from one atom in the circuit to the next atom


Correct Option: A
Explanation:

In a DC circuit , when switch is closed , the free electrons in wire are drifted from negative plate of the battery to positive plate.

The direction of current in a conductor is in the direction of flow of

  1. Electrons

  2. Atom

  3. Positive charge

  4. None


Correct Option: C
Explanation:

Conventionally, the current flows in the direction of flow of positive charge or opposite to the flow of negative charge (electrons).

The direction of current is taken as 

  1. The opposite to the direction of flow of neutrons.

  2. The opposite to the direction of flow of protons.

  3. Opposite to the direction of flow of electrons

  4. All


Correct Option: C
Explanation:

Direction of current is taken as direction of flow of positive charge.
Opposite to the direction of flow of electrons.

Direction of current is taken opposite to the direction of flow of .....

  1. holes

  2. electrons

  3. neurons

  4. protons


Correct Option: B
Explanation:

Electrons are negatively charged particles. So, by convention, the direction of current is considered as the opposite to the direction of motion of electrons.

Electric current is due to drift of electrons in

  1. Metallic conductors

  2. Semiconductors

  3. Both (a) and (b) above

  4. None of the above


Correct Option: A
Explanation:

Answer is A.
When an electric field is applied across the metallic conductors the randomly moving electrons are subjected to electrical forces along the direction of the field. Due to this field, the electrons do not give up their randomness of motion, but they will be shifting towards higher potential. That means the electrons will drift towards higher potential along with their random motions. 
In semiconductors, in addition to electrons, the travelling vacancies in the valence-band electron population (called 'holes'), act as mobile positive charges and are treated as charge carriers. Electrons and holes are the charge carriers in semiconductors.
Hence, e
lectric current is due to drift of electrons in metallic conductors.

In a series circuit.

  1. Current flow is same in all the resistors of the circuit.

  2. Potential difference across each resistor in the circuit is same.

  3. Both (1) and (2)

  4. None of these


Correct Option: A
Explanation:

In series connection same current will flow through each one of them.

State whether given statement is True or False
Conventional current always flows from a body having high electron density to body having to body having low electron density.

  1. True

  2. False


Correct Option: B
Explanation:

Conventional Current assumes that current flows out of the positive terminal, through the circuit and into the negative terminal of the source. This was the convention chosen during the discovery of electricity.
Not from high electron density to low electron density.

In case of electronic current the charge flows from negatively charged body to the positively charged body. The body which is at higher potential is 

  1. negatively charged body

  2. positively charged body

  3. both are at same potential

  4. none of these


Correct Option: B
Explanation:

By convention a positively charged body is always at a higher potential as compared to negatively charged body . If positive charges like protons or positive ions are free to move they would move from higher potential point to lower potential point.

In case of electronic current the charge flows from negatively charged body to the positively charged body. The body which is at higher potential is positively charged body

Three resistors each of $10 \Omega$ are connected in series to a battery of potential difference 150 v. The current flowing through it is ..... A.

  1. 45

  2. 5

  3. 15

  4. 20


Correct Option: B
Explanation:

Current through a resistance (R) is given by, $V=i*R _{eq}$
$i=150/30$
$i=5$ ampere

A big hallow metal sphere $A$ is charged to $100$ volts and another smaller hollow sphere $B$ is charged to $50$ volts. If B is put inside $A$ and joined with a metallic wire, then the direction of charge flow:-

  1. is from $A$ to $B$

  2. is from $B$ to $A$

  3. to charge flows

  4. depends on the radii of spheres


Correct Option: A

A DC current flows through a vertical wire in the downward direction. For an observer looking at the wire, the direction of magnetic field at a point between him and the wire is:

  1. Upward

  2. To the right

  3. To the left

  4. Downward


Correct Option: B

An aluminium (Al) rod with area of cross-section $4\times 10^{-6}m^2$ has a current of 5A. Flowing through it. Find the drift velocity of electron in the rod. Density of $Al=2.7\times 10^3kgm^{-3}$ and atomic wt.=27. Assume that each Al atom provides one electron.

  1. $8.6\times 10^{-4}ms^{-1}$

  2. $6.2\times 10^{-4}ms^{-1}$

  3. $1.2\times 10^{-4}ms^{-1}$

  4. $3.8\times 10^{-3}ms^{-1}$


Correct Option: C

When you flip a switch to turn on a light, the delay before the light turns on is determined by :

  1. The speed of the electric fields moving in the wire.

  2. the drift speed of the electrons in the wire.

  3. the number of electron collisions per second in the wire.

  4. none of these, since the light comes instantly.


Correct Option: C

A vertical wire carries a current in upward direction. If an electron beam sent horizontally towards the wire, then it will deflected.

  1. vertically downwards and perpendicular to the plane of the paper

  2. vertically upwards and perpendicular to the plane of the paper

  3. In the plane of the paper

  4. No deflection


Correct Option: A

If the strenath of the majestic field produced $10 \mathrm { cm }$ away from a infinitely long straight conductor is $10 ^ { - 5 } \text { weber/m } ^ { 2 }$ the value of the current flowing in the conductor will be:

  1. $5\ ampere$

  2. $10\ ampere$

  3. $500\ ampere$

  4. $1000\ ampere$


Correct Option: A

If current density in a conducting wire is proportional to the distance r from the axis of the conductor, then find magnetic field at the position r<R , where R is the radius of cross section of the conductor.('i'is the current in conducting wire)

  1. $ \frac { \mu _0ir^2 }{2 \pi R^3} $

  2. $ \frac { \mu _0ir^2 }{4 \pi R^3} $

  3. $ \frac { \mu _0ir^2 }{2 \pi R^2} $

  4. $ \frac { \mu _0ir^2 }{2 \pi R^4} $


Correct Option: A

Electric current flows from positive terminal of battery to negative terminal.

  1. True

  2. False


Correct Option: A

Two conducting parallel plates areseparated by a distance of 0.001$\mathrm { m } . \mathrm { A } 9 \mathrm { V }$battery is connected across the plates.Find out the electric field between the plates? 

  1. 9000$\mathrm { V } / \mathrm { m }$

  2. 900$\mathrm { Vim }$

  3. 9$\mathrm { V } / \mathrm { m }$

  4. .9$\mathrm { V } / \mathrm { m }$


Correct Option: A

The number of free electrons passing through the filament of an electric lamp is one hour when the current through the filament is 0.32 A will be 

  1. $3\times { 10 }^{ 22 }$

  2. $2\times { 10 }^{ 26 }$

  3. $7.2\times { 10 }^{ 19 }$

  4. $7.2\times { 10 }^{ 21 }$


Correct Option: D

The current density $ \bar { j }  $ at cross-sectional area $ \bar { A } = (2 \hat {i} + 4 \hat {j} )mm^{-2}$  is $(2 \hat {j} + 2 \hat {k} ) A m^{-2} $ The current following through the cross-sectional area is

  1. $ 12 \mu A $

  2. $ 8 \mu A $

  3. $ 4 \mu A $

  4. zero


Correct Option: B

A flow of $10^{12}$ electrons per minute in a conducting wire constitutes a current of 

  1. $1.6 \times 10^{-7}\, A$

  2. $1.6 \times 10^{-8}\, A$

  3. $2.67 \times 10^{-9}\, A$

  4. `$2.67 \times 10^{-10}\, A$


Correct Option: C

If 1 mole of electrons contains $ 6.02 \times 10^{23} $ electrons, the value of faraday constant, F, in coul/mole is :

  1. $ \frac {96320}{2} $

  2. $ 96320 \times 2 $

  3. 96320

  4. $ 6.6 \times 10^{19} $


Correct Option: A

The number of electrons striking the screen of CR is $7.5\times 10^{15}$ in 10 s. Calculate the electric current

  1. $1.2\times10^{-4}$

  2. $7.5\times10^{-4}$

  3. $1.6\times10^{-4}$

  4. $1.2\times10^{-5}$


Correct Option: A

In a conductor, $6.25\, \times\, 10^{16}$ electrons flow from its end A to B in 2 s. Which is the current flowing through conductor? $(e\, =\, 1.6\, \times\, 10^{-19}\, C)$  

  1. $5 mA$ from B to A.

  2. $5 mA$ from A to B.

  3. $10 mA$ from A to B.

  4. $10 mA$ from B to A.


Correct Option: A
Explanation:

In the question, it is given that the charge of an electron is $e=1.6\times { 10 }^{ -19 }\quad C$.

Therefore, the total charge flowing through the wire in 2 seconds will be given as $6.25\times { 10 }^{ 16 }\times 1.6\times { 10 }^{ -19 }\quad C\quad =10\times { 10 }^{ -3 }\quad C$.

The rate of flow of charge is therefore $\dfrac { 10\times { 10 }^{ -3 } \  C }{ 2  \ seconds\quad  } =5\times { 10 }^{ -3 }\quad C/s$.

one C/s = one amp.

Hence, the current flowing through a conductor is $0.0005 A$, that is $5 mA$.

If the electric potential difference between the two points is $V$ and resistance $R$, then the current between the points will be:

  1. $VR$

  2. $V/R$

  3. $VR^2$

  4. $V/R^2$


Correct Option: B
Explanation:

Ohm's law states that voltage drop across conductor is proportional current in it.

$ V \propto I$
$ V= IR$
The proportionality constant is $R$ which known as resistance of conductor
$I= \dfrac{V}{R}$

What is the approximate resistance setting of a rheostat in which $650 mA$ of current flows with a $150 V$ source?

  1. $230 ohm$

  2. $56 ohm$

  3. $15 ohm$

  4. $13 ohm$


Correct Option: A
Explanation:

$R=\dfrac{E}{I}$


$\implies R=\dfrac{150}{650\times 10^{-3}}$

$\implies R\approx 230\Omega$

Answer_(A)

If 18400 C of charge flows through an air conditioning unit every hour, what current does it draw?

  1. 5.11  A

  2. 5.8 A

  3. 4.1 A

  4. 6 A


Correct Option: A
Explanation:

Current is defined as charge flow per unit time .


$I=\dfrac{Q}{t}$, here $t=3600 sec$

So $I=\dfrac{18400}{3600}=5.11\ A$

An electric current of $5 A$ is divided into three branches forming a parallel combination. The length of the wire in three branches in the ratio $2:3:4$ and their diameter ratio $3:4:5$. Find the current ratio in three branches. 

  1. $1.5:2:1.3$

  2. $1.4:1.66:1.94$

  3. $1:2:1$

  4. $1:1:1$


Correct Option: B
Explanation:

Resistance $R=\rho l/A, A=\pi d^2/4$ is directly proportional to the length and inversely proportional to the Area, i.e., directly proportional to the square of the diameter.


As length are in ratio $2:3:4$ and diameter are in ratio $3:4:5$.

So the resistance are in ratio $2/3^2:3/4^2:4/5^2=2/9:3/16:4/25$

By ohm's law, current is inversely proportional to the resistance, so current is 

in ratio $9/2:16/3:25/4$

Dividing the total current $5A$ in this ratio, we get current ratios as:
$1.4:1.66:1.94$

Which of the cables, one rated 5 A and the other 15 A will be of thicker wire?

  1. 15 A cable.

  2. 5 A cable

  3. both cables

  4. nothing to say.


Correct Option: A
Explanation:

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 15 A rated wire is the thicker wire as more amount of current flow through it than the 5 A rated wire.

A cell of e.m.f. $\varepsilon$ and internal resistance $r$ is used to send current to an external resistance R. The current drawn from the cell is :

  1. $\displaystyle \frac{\varepsilon}{(R\, +\, r)}$

  2. $\displaystyle \frac{\varepsilon Rr}{R+r}$

  3. $\displaystyle \frac{\varepsilon R}{R+r}$

  4. $\displaystyle \frac{\varepsilon r}{R+r}$


Correct Option: A
Explanation:
Batteries and cells have an  internal resistance (r) which is measured in ohms. When electricity flows around a circuit, the internal resistance of the cell itself resists the flow of current and so thermal (heat) energy is wasted in the cell itself.

$\varepsilon =I(R+r)$

where,

$\varepsilon $ = electromotive force in volts, V

I = current in amperes, A

R = resistance of the load in the circuit in ohms,

r = internal resistance of the cell in ohms.

The above equation can be written as $I=\dfrac { \varepsilon  }{ R+r } $.

Hence, the expression for the current drawn from the cell is $I=\dfrac { \varepsilon  }{ R+r } $.

In an electric circuit containing a battery, the charge (assumed positive) inside the battery

  1. always goes from the positive terminal to the negative terminal.

  2. may go from the positive terminal to the negative terminal.

  3. always goes from the negative terminal to the positive terminal.

  4. does not move.


Correct Option: C
Explanation:

Inside the battery or cell, the positive charge move from negative terminal (lower potential) to positive terminal (higher potential) of the battery. While in external circuit the positive charge move from positive terminal to negative terminal of the battery.Hence correct option is C

 If 'n' electrons flow through a cross-section of a conductor in time t and charge on an electron is 'e', then the current in the conductor would be :

  1. $\displaystyle \frac{ne}{t}$

  2. $\displaystyle \frac{ne^2}{t}$

  3. $\displaystyle \frac{e}{t}$

  4. $\displaystyle \frac{n}{et}$


Correct Option: A
Explanation:

Consider a conductor of length of $L$ and cross sectional area $A$. 

When an electric field $E$ is applied across it, the electrons are drifted opposite to the applied field. 
Volume of a conductor $= LA =1$ in this case. 
Let $n$ be the number of free electrons per unit volume of conductor.
Total charge on all the electrons in the conductor $= nLAe$ 
where, $e$ is the charge of each electron.

$\Rightarrow  q = nLAe = neAL$ 

But current, $I=\dfrac { q }{ t } =\dfrac { neAL }{ t } =\dfrac { ne }{ t } \quad as\quad AL=1$

Sulphate ions move toward

  1. copper electrode

  2. battery

  3. electrolyte

  4. zinc electrode


Correct Option: D
Explanation:

Sulphate ions move toward zinc electrode.
Oxidation half reaction occurs at anode.
$\displaystyle Zn \rightarrow Zn^{2+} +2e^-$
Positively charged Zn(II) ions enter anode solution. To maintain electrical neutrality, sulphate ions move toward zinc electrode.

In a cell, by convention, charge is taken to be flowing from :

  1. positive electrode to negative electrode

  2. negative electrode to positive electrode

  3. both A and B

  4. none of the above


Correct Option: A
Explanation:

Conventionally, movement (flow) of positive charge is considered and because, unlike charge repel each other, positive charge moves from positive electrode to negative electrode inside the cell. Hence option A is correct.

Two conductors $A$ and $B$ are joined by a copper wire.  If $A$ is positively charged and $B$ is uncharged, the direction of flow of electrons is 

  1. $B$ to $A$

  2. $A$ to $B$

  3. no flow

  4. none of these.


Correct Option: A
Explanation:

The current in the wire is due to the drifting of electrons inside a wire in a direction opposite to the flow of electrons. During their drifting they collide with their atoms vibrating about their mean position and lose some of kinetic energy to the vibrating atoms. The electrons are negatively charged particles and so, the electrons move towards the positively charged conductor A.
Hence, the direction of the flow of electrons in the copper wire is from B to A.

The chemical reaction due to passage of electric current depends on:

  1. electrodes.

  2. magnitude of current.

  3. density of liquid.

  4. all of the above.


Correct Option: A
Explanation:

The chemical reaction due to passage of electric current depends on electrodes.
For example, during electrolysis of aqueous copper sulphate solution using platinum electrodes will give oxygen gas at anode.
On the other hand, during electrolysis of aqueous copper sulphate solution using copper electrodes will oxide Cu to Cu(II) ions at anode.

Conventionally, the direction of the current is taken as

  1. the direction of flow to negative charge

  2. the direction of flow of atoms

  3. the direction of flow of molecules

  4. the direction of flow of positive charge


Correct Option: D
Explanation:

Conventionally the direction of flow of current is taken to be the direction of flow of positive charges.


In wire, electrons possessing negative charges flow and positive charged kernel are at rest.
And, hence the direction of flow of current is opposite to the direction of flow of electrons in wires.

Answer-(D)

It is possible to measure the passage of $50$ electrons per second with a certain sensitive device. This corresponds to a current of :

  1. $8 \times 10^{-18} A$

  2. $1.6 \times 10^{-20} A$

  3. $8 \times 10^{-20} A$

  4. $1.6 \times 10^{-19} A$


Correct Option: A
Explanation:


Let number of electrons per second be n.
Given,
$e = 1.6 \times 10^{-19} C$ ,  $n =50 $
The current is defined as rate of flow of charge,
$I = \dfrac{q}{t} $ 
Hence,
$I = n \times e $

Substituting values,
$I = 50 \times 1.6\times 10^{-19} = 8 \times 10^{-18} A $

Conventionally, the direction of the current is taken as the direction of flow

  1. to negative charge

  2. the direction of flow of atoms

  3. of molecules

  4. of positive charge


Correct Option: D
Explanation:

Conventional Current assumes that current flows out of the positive terminal, through the circuit and goes into the negative terminal of the source.

it's not absolute direction of current it is just conventional which is used to describe the direction of current in electrical circuits.

A particle of mass $2\ g$ and charge $1\ \mu C$ is held at a distance of $1\ m$ from a fixed charge of $1\ mC.$ If the particle of released it will be repelled. Speed  of the particle when it is at a distance of $10\ m$ from the fixed charge is

  1. $100\ m/s$

  2. $90\ m/s$

  3. $60\ m/s$

  4. $45\ m/s$


Correct Option: B
Explanation:

energy of the whole system will be conserved .


so the change in the potential energy of the system will be converted into the kinetic energy of the particle 

$K(q _{1}*q _{2})/(1/r _{1}-1/r _{2})$  $=$  $(m*v^{2})/2$


substituting the values will give 

$V = 90$ $m/s$

On a bulb is written 220 volt and 60 watt. Find out the resistance of the bulb and the value of the current flowing through it:

  1. $806.66 ohm\ and\ 0.27 ampere$

  2. $500 ohm \ and\ 2 amphere$

  3. $200 ohm  \ and\ 4 ampere$

  4. $100 ohm \ and\ 1 ampere$


Correct Option: A
Explanation:

$R=\dfrac {V^2}{P}=\dfrac {(60^2)}{220}$
$=806.66 \Omega$
$I=\dfrac {P}{V}$
$=\dfrac {6-0}{220}=0.27$

In electrolysis, mass of the substance liberated at cathode is proportional to 

  1. strength of the current passed.

  2. time of passage of current.

  3. quantity of electricity passed.

  4. none of these


Correct Option: C
Explanation:

According to the first law of electrolysis the mass of of substance liberated at cathode is proportional to the quantity of electric charge passed through it or indirectly it's proportional to the quantity of  electricity  passed. 

$\because$ $m= k \times q$

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