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A galvanometer is tested shown in figure, in the circuit, where E = 1.5 V, R1 = 1.0 ohm, R2 = 2500 ohm and R3 is variable. With R3 set at 450 ohm, the galvanometer deflection is 140 mm and with R3 set at 950 ohm, the galvanometer deflection is 70 mm. The resistance of t he galvanometer is ___________
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- 55
- 25
- 49
- 59
Correct Option: C
It is simple resistive circuit calculation.
| Ic = | |||
| 1 + R3 + RG | 2500 + | ||
| 1(R3 + RG) | |||
From the given data,
| 1 + 450 + RG | 2500 + | ||
| 1(450 + RG) | |||
| = | |||
| 1 + 450 + RG | 2500 + | ||
| 1 + 950 + RG | |||
or 2500 (451 + RG) + 450 + RG = 2500 (951+ RG) + 50
or 2501 RG = 2500 (951 – 902) + 50
or RG = 49 ohms.
