Tag: physics

Questions Related to physics

The filament of bulb offers ______ resistance to electric current.

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

  1. no

  2. low

  3. high

  4. very low

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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 :

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

  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

Show answer
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

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

  1. Thin wire with many coils

  2. Thick wire with many coils

  3. Thin straight wire

  4. Thick strength wire

Show answer
Correct Option: A
Explanation:

Filaments in incandescent light bulbs are made of tungsten. When electric current goes through the filament, the 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 ____________ .

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

  1. Boiling point

  2. Melting point

  3. freezing point

  4. pressure

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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?

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

  1. High melting point

  2. Low melting point

  3. Non-corrosive

  4. high temperature resistance

Show answer
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?

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

  1. Tungstan

  2. Tin

  3. Lead

  4. Steel

Show answer
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?

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

  1. Large current flowing through filament

  2. Less current flowing through filament

  3. Corrosion from air

  4. Expansion because of heat produced

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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?

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

  1. 25 W bulb

  2. 100 W bulb

  3. Both bulb will glow brighter

  4. None will glow brighter

Show answer
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

An electric bell has a resistance of $5 \Omega$ and requires a current of $0.25\ A$ to work it. Assuming that the resistance of the bell wire is $1 \Omega$ per $15m$ and that the bell push is $90m$ distance from the bell. How many cells each of emf $1.4V$ and internal resistance $2 \Omega$, will be required to work the circuit.

physics electric current and its effects electric bell the magnetic effect of a current current electricity and magnetism

  1. $3$

  2. $4$

  3. $5$

  4. $Can't\ be\ determined$

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Correct Option: C

Name one device that uses an electromagnet.

physics electric current and its effects electric bell the magnetic effect of a current current electricity and magnetism

  1. Electric bell

  2. Barometer

  3. Lactometer

  4. All the above

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Correct Option: A