Question

A.C measuring instruments measures:
A. Peak value.
B. Rms value
C. Any value
D. Average value.

Answer 1

The electric power generated used in the world is in the form of A.C i.e. alternating current (or voltages). An ammeter is an electrical instrument through which you can measure the value of current flowing in the circuit. Also, it depends on the value attained by one complete cycle which is known as peak value.

Complete step-by-step answer:
Definition: An alternating current (A.C) is defined as that which changes its magnitude and direction periodically.
There are three types of measuring instruments: electrical instruments, electronic instruments, mechanical instruments.

In the above figure ${{I}^{2}}$ is the time average quantity.
From the above fig., R.m.s value of A.C, and it is given by expression:
${{I}_{v}}={{I}_{0}}/\sqrt{2}$.
This gives virtual or root mean square value of the Alternating current in terms of peak value.
Peak value is the maximum value attained during one complete cycle of alternating current or voltage.
Therefore, ${{I}_{v}}=70.7\%{{I}_{0}}$
I.e. rms value of A.C is 70.7% of its peak value.
In other words, we can say that the r.m.s. value is the effective value of varying currents and voltages. Also the time average value of one complete cycle is always zero.
Since the magnitude of both current and voltages varies with time interval.
Now we will calculate r.m.s value of alternating voltage, and it is given as:
${{E}_{v}}={{E}_{0}}/\sqrt{2}$
In Punjab, the virtual value of alternating voltage supplied in our houses is 220V.
Therefore,
$\begin{aligned} & {{E}_{0}}=\sqrt{2}\times 220V \\\ & {{E}_{0}}=1.411\times 220 \\\ & {{E}_{0}}=311V \\\ \end{aligned}$
So, the peak value of alternating voltage is 311V.
Hence, we conclude that the A.C measuring instruments measures rms value.

So, the correct answer is “Option B”.

Note: The instruments used to measure any quantity are known as measuring instruments. A.C measuring instruments measures alternating current and alternating voltages. R.m.s value is measured from A.C measuring instruments. The r.m.s value of Alternating current and voltages depends on its peak value.