An ac ammeter is used to measure current in a circuit. When a given direct current passes through the circuit, the ac ammeter reads 6 A. When another alternating current passes through the circuit, the ac ammeter reads 8A. Then find the reading of this ammeter, if dc and ac flow through the circuit simultaneously.
Answers & Comments
Quantity of the heat liberated in the ammeter o resistance R
(i) Due to direct current of 3A=J32R
(ii) Due to alternate current of 4A=J42R
Total heat produced per second
=3A=J32R+4A=J42R=J25R
Let the equivalent alternating current be I virtual ampere.
∴JI2R=J25R
or I=5A
~ Priyanshu