JEE Main & Advanced
JEE Main Paper (Held on 08-4-2019 Afternoon)
question_answer
In the circuit shown, a four-wire potentiometer is made of a 400 cm long wire, which extends between A and B. The resistance per unit length of the potentiometer wire is \[r=0.01\Omega /cm.\]. If an ideal voltmeter is connected as shown with jockey J at 50 cm from end A, the expected reading of the voltmeter will be :- [JEE Main 8-4-2019 Afternoon]
A)0.20 V
B)0.25 V
C)0.75 V
D) 0.50V
Correct Answer:
B
Solution :
Resistance of wire \[AB=400\times 0.01=4\Omega \]\[i=\frac{3}{6}=0.5A\] Now voltmeter reading = i (Resistance of 50 cm length) \[=\left( 0.5A \right)\left( 0.01\times 50 \right)=0.25\] volt