Question 12: The terminal voltage of the battery, whose emf is 10 V and internal resistance 1 \Omega, when connected through an external resistance of 4 \Omega as shown in the figure.
(1) 4 V
(2) 6 V
(3) 8 V
(4) 10 V
Answer: Option (3)
Explanation:
The battery of emf E and internal resistance r is connected to an external resistance R.
The total resistance of the circuit is
R_{\text{total}}=R+r=4+1=5\ \Omega.
The current flowing in the circuit is given by
I=\frac{E}{R_{\text{total}}}=\frac{10}{5}=2\ \mathrm{A}.
The terminal voltage of the battery is the potential difference across the external resistance.
Thus, the terminal voltage is
V=IR=2\times4=8\ \mathrm{V}.
Therefore, the terminal voltage of the battery is 8 V.
Hence, the correct answer is option (3).