JEE Main201912 Jan 2019Morning ShiftPhysicsCurrent ElectricityActual
The galvanometer deflection, when key K 1 is closed but K 2 is open, equals θ 0 (see figure). On closing K 2 also and adjusting R 2 to 5 Ω , the deflection in galvanometer becomes θ 0 5 . The resistance of the galvanometer is, then, given by [Neglect the internal resistance of battery]:
Options
- A12 Ω
- B22 Ω
- C5 Ω
- D25 Ω
Correct answer
B. 22 Ω
Step-by-step solution
θ 0 ∝ i G ⇒ θ 0 C = i G I-case C θ 0 = V 220 + R ......(i) II-case C θ 0 5 = V 220 + 5 R 5 + R × 5 5 + R ....(ii) From (i) and (ii) R = 22 Ω