Question

If $G$, ${r_A}$ and ${r_V}$ denote the internal resistances of a galvanometer, an ammeter, and a voltmeter respectively, the correct relationship among them is
(A) $G < {r_A} < {r_V}$
(B) ${r_A} < {r_V} < G$
(C) ${r_A} < G < {r_V}$
(D) ${r_V} < {r_A} < G$

Answer 1

Hint: We will first understand the principle and working of the given electrical instruments. All three instruments are very useful in electrical engineering and electrical science. They work on some specific principle associated with them.

Complete step-by-step solution:
A galvanometer is an electronic device that is used to measure the magnitude of electric current and that can detect small electric current flowing in the circuit. The galvanometer consists of a magnetic needle that usually shows the intensity of current by the moment of a coil in a magnetic field and hence it is an important part of a galvanometer.
A voltmeter is a device that measures the voltage or potential difference between the two terminals of the circuit. The unit of potential difference in volts. For an ideal voltmeter, it is considered that its ideal resistance should be very high or equal to infinity.
 An ammeter is also known as Ampere-meter is an instrument that measures the amount of electric current in the circuit or can be said to be its ampere value. It is always connected in series with the battery. For an ideal ammeter, it is considered that its internal resistance must be very low or equals to zero
Hence if we consider that the resistance of the galvanometer is $G$ and the internal resistance of voltmeter is ${r_V}$ and the internal resistance of ammeter is given as ${r_A}$, then from our discussion it can be said that for the case of ammeter the resistance must be very less or equal to zero while for voltmeter the resistance must to very high, and the internal resistance of galvanometer comes in between both of them, hence the correct series of their resistance can be given as ${r_A} < G < {r_V}$.

Hence option (C) is the correct answer.

Note: The galvanometer is always connected in series with the battery in the circuit similarly an ammeter is always connected in series with the battery while a voltmeter is connected in parallel with the battery or device across which we want to measure the voltage.