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Bulb - class-VI

Description: bulb
Number of Questions: 28
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Tags: electrical appliances in everyday life simple electric circuits electricity and circuits electric circuit physics
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State whether given statement is True or False
An electric bulb is a source of electricity.

  1. True

  2. False


Correct Option: B
Explanation:

Electric Bulb is a source of light. Hence above statement is False.

Fill in the blanks:

Pure tungsten has _________.

  1. low resistivity and a high melting point.

  2. high resistivity and a high melting point.

  3. high resistivity and a low melting point.

  4. low resistivity and a low melting point.


Correct Option: B
Explanation:

tungsten has a high melting point and is able to withstand heat and corrosion. Tungsten is one of the most durable types of filaments used in light bulbs. It must be exposed to very high temperatures before melting, and only carbon arc has a higher heat resistance level than tungsten.

 An electric bulb converts electrical energy into 

  1. sound energy

  2. mechanical energy

  3. nuclear energy

  4. none of these


Correct Option: D
Explanation:

Electric bulb uses the  heating effect of current.when current is passed, electric bulbs has a tungsten filament which gets heated with the flow of current and brighten up, the filament having a high value of resistance heated up , more the heat more will be the light.

A $2$ KW electric heater is connected to a $400$ V $50$ Hz mains supply. The peak value of electric current flowing in the circuit is approximately (take $\sqrt2=1.4$)

  1. $2.5$ A

  2. $5.0$ A

  3. $7$ A

  4. $10$ A


Correct Option: A

A building has $10$ bulbs of $40W$, $5$ bulbs of $100W$, $5$ fans of SOW and one heater of $1$ kilowatt.Every day bulbs are using for $5$ hours, fans are using for $8$ hours and heater is using for $1$ hour. The electric mains voltage is $220 V$. Calculate:

  1. Maximum power of the electric circuit in the building

  2. The minimum capacity of main fuse in the building and

  3. The cost of consumed electric energy the rate of Rs $5$ per unit in a week

  4. Maximum power of the electric circuit in the building.


Correct Option: C

_________ wire is used in an electric bulb.

  1. copper

  2. tungsten

  3. iron

  4. aluminium


Correct Option: B
Explanation:

It’s usually tungsten, although carbon or carbonized fibers (bamboo or hair) was occasionally used in older bulbs.


LEDs are extensively used to replace bulbs because:

  1. it consumes less electricity.

  2. have longer life.

  3. has more power.

  4. all of the above.


Correct Option: D
Explanation:
Advantages of LEDS over bulbs:
1. Energy efficient
2. Cost saving
3. Longer life span

When the current passes through the filament, it gets heated to incandescence and give light while the connecting wires are not heated because

  1. The connecting wires are good conductor of heat while the filament is bad conductor.

  2. The connecting wires are of low resistance while the filament is of high risistance.

  3. The density of connecting wires is less than that of the filament.

  4. The connecting wires are bad conductor of heat while the filament is good conductor.


Correct Option: B
Explanation:
An incandescent light bulbincandescent lamp or incandescent light globe is an electric light with a wire filament heated to a high temperature, by passing an electric current through it, until it glows with visible light (incandescence).The hot filament is protected from oxidation with a glass or quartz bulb that is filled with inert gas or evacuated. In a halogen lamp, filament evaporation is prevented by a chemical process that redeposits metal vapor onto the filament, extending its life.
The resistance of wires used inside bulb is very high so on passing current it glows.

A bulb of 100W means that it will consume electrical energy at the rate of

  1. 100 KJ per second

  2. 100 KJ per hour

  3. 100 joules per second

  4. 100 joules per hour


Correct Option: C
Explanation:

$100W$ means $100J$ of energy is consumed per second of time.


Answer-(C)

The bulbs which emit a bluish light, are

  1. filled with argon

  2. filled with nitrogen

  3. vacuum bulbs

  4. coated from inside with a light blue colour


Correct Option: A
Explanation:

Because atoms and molecules can exist only in certain specific energy states, the energy emitted by the excited molecule is limited to differences between these states. Only certain energies of light are emitted. The colour of the glow is determined by the energy of the emitted light. and for argon its bluish

The filament of an electric bulb is of tungsten because

  1. its resistance is negligible.

  2. it is cheaper.

  3. its melting point is high.

  4. filament is easily made.


Correct Option: C
Explanation:

Incandescent light bulbs use heat generated by the resistance of the filament to create light. to get white light you need the filament to reach 2700-3300 K to give off white yellow light.

The reason tungsten is used is because it has the highest melting temperature of any element at 3600 K.

To generate a lot of heat you need a big resistance. Resistance(R) is dependent on resistivity ($\rho$) but also on the length (l) of the wire and the width (w).

R $=\dfrac{\rho \times l}{A} $

Having a big resistivity helps to create a big resistance but since you can change the thickness and length of the filament in light bulb (the filament is looped to increase the length) you can control the resistance. 

An electric bulb is filled with :

  1. hydrogen

  2. oxygen and hydrogen

  3. electrical energy

  4. nitrogen and argon


Correct Option: D
Explanation:

Incandescent light bulbs are filled with an inert gas like nitrogen, argon, or krypton - so that the filament doesn't catch fire. Early ones were a vacuum. Flourecent lamps are filled with an inert gas plus mercury vapour or neon, which glows ultra-violet when charged. The inside of the bulb is painted to give it colour.

The filament of bulb offers ______ resistance to electric current.

  1. no

  2. low

  3. high

  4. very low


Correct Option: C
Explanation:

The filament of bulb has high resistance so the filament heats up due to current passing through (${ I }^{ 2 }R$ losses )  and due to its heating , the electrons change their energy states and photons in visible spectrum are emitted . more the losses , more would be the light.that's why filament of bulb offers high resistance.

When current is passed through an electric bulb, its filament glows, but the wire leading current to the bulb does not glow because :

  1. Less current flows in the leading wire as compared to that in the filament

  2. The leading wire has more resistance than the filament

  3. The leading wire has less resistance than the filament

  4. Filament has coating of fluorescent material over it


Correct Option: C
Explanation:

The leading wire is usually made with conductors such as copper and aluminium, therefore have less resistance than the filament which is usually made with tungsten and has a high resistance.
Due to this the power lost P $ =I^{2}R $ is greater for filament which is visible as light(and also heat).

The filament of a bulb is usually a

  1. Thin wire with many coils

  2. Thick wire with many coils

  3. Thin straight wire

  4. Thick strength wire


Correct Option: A
Explanation:

Filaments in incandescent light bulbs are made of tungsten. When electric current goes through the filamentthe filament glows. It may also be known as the electron emitting element in a vacuum tube. To make the bulb produce more light,the filament is usually made of coils of fine wire, also known as the coiled coil.

The material which is used as a filament for bulb has high ____________ .

  1. Boiling point

  2. Melting point

  3. freezing point

  4. pressure


Correct Option: B
Explanation:
The melting point of filament of a bulb is very high because the bulb begins to glow only when the filament is heated to a high temperature,and it becomes incandescent (bright) without melting.This happens only when the material of the filament has a high melting point.Hence, the material used in the filament of an electric bulb must have a high melting point. For example Tungsten

Which of the following is/are properties of filament of bulb?

  1. High melting point

  2. Low melting point

  3. Non-corrosive

  4. high temperature resistance


Correct Option: A,C,D
Explanation:
The filament is an important part of incandescent lamp. The life of an incandescent lamp, depends on its filament. The filament material must have following merits-
  1. High melting point.
  2. Low vapor pressure.
  3. Free from oxidation in inert gas (i.e. argon, nitrogen etc.) medium at operating temperature.
  4. High resistivity.
  5. Low thermal coefficient of expansion.

Which of the following things can be used as a filament of electric bulb?

  1. Tungstan

  2. Tin

  3. Lead

  4. Steel


Correct Option: A
Explanation:

Tungsten metal is selected for making filaments of lamp bulbs because tungsten can sustain high temperatures and it has high melting point, combined with the fact that it also has high resistivity. They do not oxidize easily at high temperatures.

Which of the following will create breaking of filament of a bulb?

  1. Large current flowing through filament

  2. Less current flowing through filament

  3. Corrosion from air

  4. Expansion because of heat produced


Correct Option: A,D
Explanation:

Large current flowing through filament,Expansion because of heat produced will create breaking of filament of a bulb
The filament heats and gives off light. Over time, the filament oxidizes and becomes more and more brittle, until it breaks apart and the bulb goes out. ... Tungsten gains resistance as it heats. Resistance is the amount of 'push back' a material has against an electric current

A 25W and 100W bulb are joined in series and connected to the mains. Which bulb will glow brighter?

  1. 25 W bulb

  2. 100 W bulb

  3. Both bulb will glow brighter

  4. None will glow brighter


Correct Option: A
Explanation:

Resistance of 25 w bulb, ${R _1} \Rightarrow \frac{{{{220}^2}}}{2} = 1936\Omega $

$\begin{array}{l} { R _{ 2 } }=\frac { { { { 220 }^{ 2 } } } }{ { 100 } } =484\Omega  \ In\, \, series \ P\alpha R, \end{array}$
25 w will glow more

LEDs are extensively used to replace . bulbs because:

  1. it consumes less electricity

  2. have longer life

  3. has more power

  4. all of the above


Correct Option: D
Explanation:

A light-emitting diode (LED) is a two-lead semiconductor light source. it is a p-n junction diode, which emits light when activated. LEDs have more power, more life time and consume less electricity than a bulb, thus these are extensively used to replace bulbs.

The glowing of electric bulb is based on _________ effect of current.

  1. heating

  2. magnetic

  3. luminous

  4. none of the above


Correct Option: A
Explanation:

Answer is A.
The electric bulb has a filament called tungsten when electricity passes through this filament, it heats up and glows. This heat is generated due to the passage of electric current and the drift of electrons due to the current and the resistance it causes.
Hence, The glowing of electric bulb is based on the heating effect of electric current.

When an electric bulb breaks, there is a mild bang due to:

  1. The photo-chemical reaction between the enclosed gases.

  2. The compressed gases rushing out suddenly.

  3. The air rushing into fill the evacuated space.

  4. None of these


Correct Option: C
Explanation:

Answer is C.

When an electric bulb breaks, there is a mild bang due to the sudden air rushing into fill the evacuated space.

In the bulb there is a -

  1. Long wire

  2. Short wire

  3. Thin wire

  4. Wide wire


Correct Option: C
Explanation:

as we know $Resistance =Resistivity\dfrac{Length}{Area}$

therefore, for making resistance more the radius of the wire should be less to make area less and make resistance more. as resistance is inversely proportional to area. therefore to make bulb we need thin wire. which is capable of withstanding high temperature and have high resistance.

An electric bulb converts electrical energy into

  1. sound energy

  2. mechanical energy

  3. nuclear energy

  4. none of these


Correct Option: D
Explanation:

Due to passage of electric current, the tungsten filament of the bulb gets heated up and glows. Thus an electric bulb converts electrical energy into heat energy as well as light energy.

Hence option D is correct.

The filament of an electric bulb is of tungston because

  1. Its resistance is negligible.

  2. It is cheaper.

  3. Its melting point is high.

  4. filament is easily made.


Correct Option: C
Explanation:

Tungston has very high melting point. Thus it does not melt even when a large amount of heat is produced in the bulb due to heating effect of current. Hence it is used as a filament in the bulb.

The filament of a bulb is usually a:

  1. thin wire with many coils

  2. thick wire with many coils

  3. thin straight wire

  4. thick straight wire


Correct Option: A
Explanation:

 When electric current goes through the filamentthe filament glows. It may also be known as the electron emitting element in a vacuum tube. To make the bulb produce more light,the filament is usually made of coils of thin wire, also known as the coiled coil in order to get more emmision.

Generally, Filaments in incandescent light bulbs are made of tungsten as its melting point is very high.
Therefore, A is correct option.

The wire of an electric lamp has a:

  1. high resistance and a high melting-point

  2. high resistance and low melting-point

  3. low resistance and low melting-point

  4. low resistance


Correct Option: A
Explanation:

Answer is A.

when choosing a material for a particular application, many different properties of materials must all be considered together (such as: melting point (MP), boiling point (BP), thermal conductivity, electrical resistivity, cost, etc.). For example, while Nichrome does have a much higher resistivity than Tungsten, Tungsten has a much higher melting point than Nichrome (Nichrome MP = 1400 C, Tung MP = 3422 C). For a typical incandescent light bulb, the Tungsten filament operates at approximately 2500 Celsius; notice that this is actually above the melting point of Nichrome!
Therefore, when you compare the melting points of the materials to the operating temperatures of a light bulb, you can quickly see why Tungsten is the preferred choice for filament wires. 
Pure tungsten has some amazing properties including the highest melting point (3695 K), lowest vapor pressure, and greatest tensile strength out of all the metals.Because of these properties it is the most commonly used material for light bulb filaments.
Hence, the wire of an electric lamp has a high resistance and high melting point.

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