Question

An analog ammeter able to have a 0.5 A maximum reading is to be built using a small coil of resistance R = 20 Ω, and full scale deflection at 1 mA. What resistance should be added to this coil and how should it be connected to the coil?

Answer 1

The resistance added to this coil is 0.04 ohm in parallel.

Step-by-step explanation:

Given that,

Current I'= 0.5 A

Resistance R= 20 ohm

Deflection I= 1 mA

We need to calculate the resistance

Using ohm's law

`V = I R`

Where,

V = voltage

I =current

R = resistance

V is constant so ,

Therefore,

I R=I'R'

`R'=(I)/(I')* R`

`R'=(0.001)/(0.5)*20`

`R'=0.04\ \Omega`

Hence, The resistance added to this coil is 0.04 ohm in parallel.