Question

A galvanometer can be used as a voltmeter of a certain range by using a resistance of 180 ohm in series with it.When a resistance of 380 ohm is connected in series with it , the range is doubled. Find the resistance of it?

Answer 1

Answer:

The required resistance to be added will be R₃ = 3R₁ - 2R₂

The galvanometer resistance G = R₁ - 2R₂

Explanation :

when resistance R₁ is connected, then the galvanometer eqn can be written as:

R₁ = V/I  -  G

when resistance R₂ is connected, then the galvanometer eqn can be written as:

R₂ = V/2I  -  G

from both the eqn we get,

V/2I = R₁ - R₂

and

G = R₁ - 2R₂

when resistance R₃ is connected to make it read 2V, then the galvanometer eqn can be written as:

R₃ = 2V/I  -  G

=> R₃ = 4(R₁ - R₂) - (R₁ - 2R₂)

=> R₃ = 3R₁ - 2R₂

Answer 2

Answer:

Explanation:

Answer has been given