Question

Two identical batteries, each of emf $2V$ and internal resistance $1\Omega$, are available to produce heat in an external circuit. The maximum rate of production of heat in the external circuit will be

• A. 1 W
• B. 8 W
• C. 4 W
• D. 2 W

Answer 1

Answer: (D)

2 W

Given
$E_1=E_2=2V$
$r_1=r_2=1\Omega$
The condition for maximum rate of production of heat in the external circuit when $n(=2)$ identical cells are connected in series is
$H_{max}=n\left[\frac{(E{)}^2}{4r}\right]$
$H_{max}=2\left[\frac{2^2}{\left(4\right)\left(1\right)}\right]$
$H_{max}=2\left(1\right)=2W$