A small bulb has a resistance of 2 ohm when it is cold. It draws 0.4 ampere current from a source of 4 V and then starts glowing. Calculate the resistance when it is glowing.

Given: Resistance (R cold) = 2 Ohm

Current (I) = 0.4 Ampere

Voltage (V) = 4 V

The resistance when the bulb is glowing is calculated by using Ohm’s law.

According to Ohm’s law,

V = I x R

Substituting the values in the above equation, we get

R = 4/0.4

R = 10 Ohm


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CBSE CLASS XII Related Questions

  • 1.
    Read the following paragraph and answer the questions that follow.
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      • 2.
        A charged particle $+q$ in an electric field $\vec{E}$ experiences a force in the direction of the electric field. As a result, its kinetic energy changes. Similarly, the charged particle also experiences a force when it moves in a magnetic field $\vec{B}$. But this magnetic force is perpendicular to both velocity $\vec{v}$ of the charged particle and the magnetic field $\vec{B}$, so it cannot change the kinetic energy of the charged particle. Consider two charged particles 1 and 2 of masses $m$ and $\frac{m}{2}$ having charges $-q$ and $+2q$ respectively. They are accelerated from rest through the same potential difference $V$ and acquire kinetic energy $K_1$ and $K_2$. Then they enter in a region of uniform magnetic field $\vec{B}$ perpendicular to their velocities.


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              • 4.
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                  • 5.
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                      • 6.
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                          CBSE CLASS XII Previous Year Papers

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