Question

Consider two identical galvanometers and two identical resistors with resistance R. If the internal resistance of the galvanometers ${R_c} < R/2$, which of the following statement(s) about any one of the galvanometers is(are) true?
A. The maximum voltage range is obtained when all the components are connected in series.
B. The maximum voltage range is obtained when the two resistors and one galvanometer are connected in series, and the second galvanometer is connected in parallel to the first galvanometer.
C. The maximum current range is obtained when all the components are connected in parallel.
D. The maximum current range is obtained when the two galvanometers are connected in series and the combination in parallel with both the resistors.

Answer 1

Hint: Galvanometer is converter into voltmeter by connecting a shunt resistance in series with the galvanometer and greater the value of shunt resistance the bigger the voltage range also if the internal resistance of galvanometer is maximum then also we will get maximum range of voltage.

Complete answer:
Let's check each and every option
Option-A is correct because when we will connect all the components is series we will get maximum resistance and since current of source is kept constant while measuring the voltage therefore maximum voltage range will occur

Option-B is incorrect because if we connect the two resistors and one galvanometer are connected in series, and the second galvanometer is connected in parallel to the first galvanometer we will not get maximum resistance nor the maximum voltage range

Option-C is incorrect too because when all the components are connected in parallel we will get minimum resistance but we need maximum resistance

Option-D is incorrect too in this case too we will not get maximum resistance it will be somewhere between minimum resistance and maximum resistance but its not maximum so this option is also incorrect.

Hence, Option-A is correct.

Note: To solve such type of question you need to understand how galvanometer and external resistance are connected to get voltmeter in other words how voltmeters are made and in voltmeter larger the value of external resistance larger the voltage range, so you will have to maximize the total resistance.