Question

A milliammeter has an internal resistance of 5ohms and

Answer 1

Answer:

Rs = 0.02008 Ω = 20.08 mΩ

Explanation:

The range of an ammeter can be increased by connecting a small shunt resistance to it in a series combination. This shunt resistance can be calculated by the following formula:

$Rs = \frac{I_gR_g}{I - I_g}$

where,

$R_s$ = value of shunt resistance = ?

$I_g$ = current range of ammeter = 20 mA = 0.02 A

I = Required range of ammeter = 5 A

$R_g$ = Resistance of ammeter = 5 ohms

Therefore,

$R_s = \frac{(0.02\ A)(5\ ohms)}{5\ A-0.02\ A}$

Rs = 0.02008 Ω = 20.08 mΩ