Question

The terminal potential difference for a cell is 9.5 V when current is 2 A and 9 V when current is 1.5 A. What is the internal resistance of the cell?

• A. 4 $\Omega$
• B. 2 $\Omega$
• C. 3 $\Omega$
• D. 1 $\Omega$

Answer 1

Answer: (D)

1 $\Omega$

Answer 2

A cell gives terminal voltage V = E – I·r.

For I = 2 A: 9.5 = E – 2r
For I = 1.5 A: 9 = E – 1.5r

Subtracting the equations yields:
0. 5 = 0.5r
Thus, r = 1 $\Omega$.