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

Question

A battery of emf 12 V and internal resistance 3 \(\Omega\) is connected to an external resistor. If the current in the circuit is 0.6 A, the voltage across the external resistor will be

Answer 1

To determine the internal resistance of the cell, we can use Ohm's Law and the formula for the total voltage in a circuit, which accounts for both the external resistance (load resistance) and the internal resistance of the cell.

The given problem provides us with the following details:

Voltage of the cell, V = 2.1 \, \text{V}
Current flowing through the circuit, I = 0.2 \, \text{A}
External resistance, R = 10 \, \Omega

The formula to find the total voltage in the circuit is:

V = I \cdot (R + r)

where r is the internal resistance of the cell.

Rearranging the formula to solve for internal resistance:

r = \frac{V}{I} - R

Substituting the known values:

r = \frac{2.1}{0.2} - 10

Calculating the first part:

\frac{2.1}{0.2} = 10.5

Now, substituting back to find r:

r = 10.5 - 10 = 0.5 \, \Omega

Thus, the internal resistance of the cell is 0.5 \, \Omega.

The correct answer is therefore 0.5Ω.

Answer 2