Question

The coil of wire in a galvanometer has a resistance of RC = 71.0 Ω. The galvanometer exhibits a full-scale deflection when the current through it is 0.470 mA. A resistor is connected in series with this combination so as to produce a voltmeter. The voltmeter is to have a full-scale deflection when it measures a potential difference of 14.0 V. What is the resistance of this resistor?

Answer 1

Answer:

29716 ohms

Explanation:

Using ohm's law

V = IR where I is current in the circuit and R is the effective resistance of the circuit

V₁, across the galvanometer without the resistor = 0.00047 × 71 = 0.03337 V

Voltage across the resistor = 14 V - 0.03337 V = 13.9663 V

Voltage across the resistor = IR where R is the resistance of the resistor and I = 0.000470 A

R = 13.9663 V / 0.000470 A = 29716 ohms