Question

In the circuit, the galvanometer G shows zero deflection. If the batteries A and B have negligible internal resistance, the value of resistor R will be

• A. 100Ω
• B. 200Ω
• C. 1000Ω
• D. 500Ω

Answer 1

Answer: (A)

100Ω

Answer 2

Correct option is A)

Applying Kirchoff's law
for loop BCDFAEB: 500i = 12-2 ⇒ i = 10/500 = 1/50
when galvanometer shows zero deflection then no current flow through it.

now for loop BCDEB: 500i+Ri=2⇒ i = $\frac{12}{R+500}$

or 1/50 = 12/(R+500)

or R+500 = 600 = R=100Ω