Q 12-03-066JEE MainJEE Main 2025 (22 Jan, Shift 1)Medium
The sliding contact of a potentiometer is in the middle of the potentiometer wire having resistance $R_p = 1\ \Omega$ as shown in the figure. An external resistance of $R_e = 2\ \Omega$ is connected via the sliding contact. The electric current in the circuit is
Answer: (D) $1.0\ \text{A}$
The slider divides the wire into two halves of $0.5\ \Omega$ each.
$R_e = 2\ \Omega$ is connected between the left end of the wire and the slider, so it is in parallel with the left half:
$$R_{\parallel} = \frac{0.5\times2}{0.5+2} = 0.4\ \Omega$$
This is in series with the right half:
$$R_{total} = 0.4 + 0.5 = 0.9\ \Omega$$
$$I = \frac{0.9\ \text{V}}{0.9\ \Omega} = 1.0\ \text{A}$$
Solution by Sreeraj P, M.Sc Physics