Question

If a voltmeter, inadvertently mistaken for an ammeter, were inserted into the circuit, the current
A. Increases
B. Remains the same
C. Decreases
D. Becomes zero

Answer 1

We will use the properties of both voltmeter and ammeter respectively to find the correct answer. An ammeter is always connected in series with the circuit for current measurement and voltmeter is connected in parallel to the circuit for voltage measurement. We also know that an ammeter should have zero resistance and voltmeter should have the highest possible value of resistance for proper functioning.

Complete answer:
We know that voltmeter has maximum possible value of resistance and is always connected in parallel to the circuit while an ammeter has negligible value of resistance (close to zero) and connected in series with the circuit to function properly. We also know that the function of a voltmeter is to measure potential difference or voltage and the function of an ammeter is to measure the electric current in the circuit accurately.
Now, if the voltmeter is mistaken as an ammeter then it will be connected in series with the circuit and we know that a voltmeter has maximum possible value of resistance because of which it will start opposing the flow of electric current through the circuit and the value of electric current decreases.

Hence, option $(C)$ is the correct answer.

Note:
We should always remember that ammeter is connected in series and voltmeter in parallel with the circuit respectively. For an ideal case the resistance of voltmeter should have infinite value and the resistance of an ammeter should be zero. But in reality the values of resistance are close to infinity for voltmeter and close to zero for ammeter.