Question

Scale used in moving coil galvanometer is:
A. Function scale
B. Linear scale
C. Exponential scale
D. None of these

Answer 1

Hint: Recall the scales used for the measurement. The defection of the needle of the galvanometer is proportional to the current.

Complete step by step answer:
A galvanometer is the device mainly used in the potentiometer. It measures or detects the small current if any flowing through the electric circuit. It has a magnetic needle to show the magnitude and direction of the current as it deflects from the mean position.
Galvanometer works on the principle of deflection of coil due to presence on magnetic fields around it. The external magnetic field experiences torque which results in deflection of the coil. The deflection of the coil is proportional to the current flowing through it.
The deflection produced in the coil is balanced by the needle made up of the spring of a galvanometer. The angle through which the needle is deflected is proportional to only the current in the coil and all other quantities are constant.
Therefore, the deflection of a needle is the measure of current in the coil. Since this deflection is
proportional to the current, the scale of measurement must be linear.
For an exponential scale, the deflection of the needle must be the function of exponential form of current. But since the deflection of the needle is proportional to current, the option (C) is incorrect.

So, the correct answer is “Option B”.

Note:
Students should remember the working principle of galvanometer, potentiometer, and other instruments used for measurement of electric quantities. In a galvanometer, the deflection of a needle is the only function of current and all other quantities are constants. If any one of them is not the constant, then the reading shown by galvanometer will not be linear with the current.