Question

a moving coil galvanometer has resistance 20 ohm show full deflection for current 50mA how will you convert galvanometer to ammeter of range 20A and voltmeter of 120v​

Answer 1

Answer:

Explanation:

A moving coil galvanometer has resistance 20 ohm show full deflection for current 50mA how will you convert galvanometer to ammeter of range 20A and voltmeter of 120v​

50

convert galvanometer to ammeter of range 20A

Current Range can be extended using Shunt across (S)

50mA = 0.05 A

20 Ω

20 * 0.05 = 1 V

Current across Shunt = 20 - 0.05 = 19.95 A

20 * 0.05 = S * 19.95

=> S = 1/19.95

=> S = 0.05 Ω  ( in Parallel)

convert galvanometer to voltmeter of 120v​  ( independent of 1st change)

Can be converted using High Resistance in series

High resistance must have a  drop of 120 - 1 = 119V when

0.05 A current flows through it

0.05R = 119

=> R = 2380 Ω  (in series)

if We need to convert it to voltmeter of 120v​  after converting into 20A

Then Drop of 120 -1  = 119 V is required at 20A Current Flow

20R = 119 V

=> R = 5.95 Ω  (in series)