Question

A milliammeter has an internal resistance of 5ohms and

reads upto 20 millianmeter, cal the value of the resistance
that should beconnected to it to enable to read up to
5A

Answer 1

Rs = 0.02008 Ω = 20.08 mΩ

Step-by-step 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 = (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 = ((0.02\ A)(5\ ohms))/(5\ A-0.02\ A)`

Rs = 0.02008 Ω = 20.08 mΩ