Solveeit Logo
Login

Question

Physics Question on Resistance

The internal resistance of a 2.1 V cell which gives a current of 0.2 A through a resistance of 10 Ω is

A

1.0 Ω

B

0.2 Ω

C

0.5 Ω

D

0.8 Ω

Answer

0.5 Ω

Explanation

Solution

In the question, we have the values for external resistance, current, and voltage of the cell. As per ohm's law, these quantities are related to each other. Hence, ohm’s law will be used to calculate the internal resistanceof the cell through the values.

Formula used:

As per ohm’s law, V = I(R+r)

  • Where V is voltage,
  • I is current,
  • R is external resistance
  • r is internal resistance.

Complete step-by-step solution:

Given: Internal resistance = 2.1V, Current = 0.2A, external resistance = 10Ω.

To calculate internal resistance, we will use ohm’s law.

V = I(R+r)

2.1 = (0.2)(10+r)

⇒10+r=212⇒10+r=\frac{21}{2}

⇒r=212−10⇒r=\frac{21}{2}−10

r = 0.5 Ω

Thus, the internal resistance of the given cell is 0.5Ω.

Hence, the correct option is (C).

Note: The sum of internal and external resistance is the total resistance.