Question

An ac ammeter is used to measure currnet in a circuit. When a given direct current passes through the circuit. The ac ammeter reads 3 A. When another alternating current passes through the circuit, the ac ammeter reads 4A. Then find the reading of this ammeter (inA), if dc and ac flow through the circuit simultaneously.

Answer 1

Given:

An ac ammeter is used to measure current in a circuit. When a given direct current passes through the circuit. The ac ammeter reads 3 A. When another alternating current passes through the circuit, the ac ammeter reads 4A.  

To find:

Then find the reading of this ammeter (inA), if dc and ac flow through the circuit simultaneously.

Solution:

From given, we have,

When a given direct current passes through the circuit, the ac ammeter reads 3 A.  

I_{dc} = 3 A

When another alternating current passes through the circuit, the ac ammeter reads 4A.  

I_{ac} = 4 A

The reading of the ammeter is given by,

I = √[I_{dc}² + I_{ac}²]

I = √[3² + 4²]

I = √25

∴ I = 5 A

Therefore, the reading of this ammeter, if dc and ac flow through the circuit simultaneously is 5 A.