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 $\mathrm{R}_{\mathrm{e}}=2 \Omega$ is connected via the sliding contact.

JEE Main · 2025 · 22 Jan 2025 · Shift 1 · Current Electricity

Sliding contact of a potentiometer is in the middle of the potentiometer wire having resistance

R_{p} = 1Ω

as shown in the figure. An external resistance of

R_{e} = 2Ω

is connected via the sliding contact.

Answer: (C)

The battery of emf 0.9 V drives current through the potentiometer wire (total resistance

R_{p} = 1 Ω

). The sliding contact sits at the midpoint, splitting the wire into two

0.5 Ω

halves, and the external resistance

R_{e} = 2 Ω

is connected across the second half through the slider.

Redrawing the circuit, the first

0.5 Ω

half is in series with the parallel combination of the second

0.5 Ω

half and

R_{e} = 2 Ω

R_{p a r a l l e l} = \frac{0.5 \times 2}{0.5 + 2} = \frac{1}{2.5} = 0.4 Ω.

R_{e q} = 0.5 + 0.4 = 0.9 Ω.

The current drawn from the battery is

i = \frac{0.9 V}{0.9 Ω} = 1 A .

JEE Main · 2025 · 22 Jan 2025 · Shift 1 · Single correct option