Tag: physics

Questions Related to physics

 An electric bulb converts electrical energy into 

physics simple electric circuits bulbs bulb bulb connected to an electric cell

  1. sound energy

  2. mechanical energy

  3. nuclear energy

  4. none of these

Show answer
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 $\sqrt2=1.4$)

physics simple electric circuits bulbs bulb bulb connected to an electric cell

  1. $2.5$ A

  2. $5.0$ A

  3. $7$ A

  4. $10$ A

Show answer
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:

physics simple electric circuits bulbs bulb bulb connected to an electric cell

  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.

Show answer
Correct Option: C

_________ wire is used in an electric bulb.

physics simple electric circuits bulbs bulb bulb connected to an electric cell

  1. copper

  2. tungsten

  3. iron

  4. aluminium

Show answer
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:

physics simple electric circuits bulbs bulb bulb connected to an electric cell

  1. it consumes less electricity.

  2. have longer life.

  3. has more power.

  4. all of the above.

Show answer
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

physics simple electric circuits bulbs bulb bulb connected to an electric cell

  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.

Show answer
Correct Option: B
Explanation:
An incandescent light bulb, incandescent 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

physics simple electric circuits bulbs bulb bulb connected to an electric cell

  1. 100 KJ per second

  2. 100 KJ per hour

  3. 100 joules per second

  4. 100 joules per hour

Show answer
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

physics simple electric circuits bulbs bulb bulb connected to an electric cell

  1. filled with argon

  2. filled with nitrogen

  3. vacuum bulbs

  4. coated from inside with a light blue colour

Show answer
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

physics simple electric circuits bulbs bulb bulb connected to an electric cell

  1. its resistance is negligible.

  2. it is cheaper.

  3. its melting point is high.

  4. filament is easily made.

Show answer
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 :

physics simple electric circuits bulbs bulb bulb connected to an electric cell

  1. hydrogen

  2. oxygen and hydrogen

  3. electrical energy

  4. nitrogen and argon

Show answer
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.