Question

A galvanometer of resistance 100 Ω gives full scale deflection for a current of 1.0 mA. It is converted into an ammeter of range (0 − 1A). The resistance of the ammeter will be close to ______.

Options

• 0.1 Ω

• 0.8 Ω

• 1.0 Ω

• 10 Ω

Answer 1

A galvanometer of resistance 100 Ω gives full scale deflection for a current of 1.0 mA. It is converted into an ammeter of range (0 − 1A). The resistance of the ammeter will be close to 0.1 Ω.

Explanation:

R_G = 100 Ω, I_g = 1.0 mA = 10⁻³ A

I_gR_G = (I − I_g)R_S

`R_S = (I_gR_G)/(I - I_g)`

= `(10^-3 xx 100)/((1 - 0.001))`

= `0.1/0.999`

= 0.1 Ω