Question

Alternating current cannot be measured by DC ammeter because:
1. Alternating current cannot pass through the DC ammeter
2. Average value of complete cycle is zero
3. Alternating current changes its direction
4. None of these

Answer 1

Correct Answer - Option 2 : Average value of complete cycle is zero

CONCEPT:

Mean value:

• The average of all the instantaneous values of alternating currents over one complete cycle is called the mean value.
• The mean value of the alternating current is zero.

EXPLANATION:

• The DC ammeter measures the mean value of current and the mean value of the AC current is zero, so we cannot measure the AC current by the DC ammeter.
• Hence, option 2 is correct.

Peak value:

• The maximum value attained by an alternating current during one cycle is called its Peak value.
• It is denoted by Io.

​RMS value:

• It is that steady current which, when flows through a resistor of known resistance for a given period of time than as a result the same quantity of heat is produced by the alternating current when flows through the same resistor for the same period of time is called R.M.S or effective value of the alternating current.
• The RMS value of current is given as,

​\(\Rightarrow I_{rms}=\frac{I_{o}}{\sqrt{2}}\)