Question

Difference between ballistic galvanometer and spot galvanometer

Answer 1

ballistic galvanometer :-  A galvanometer specially designed for the measurement of the quantity of the charge displaced in a current of short duration like charging and discharging of the capacitor.
                                                         while 
spot galvanometer :-  a galvanometer specially designed for the measurement of the  small quantity of the current through the circuit. spot galvanometer is also known as reflecting galvanometer.

Answer 2

Ballistic galvanometer is a  sensitive galvanometer
.A ballistic galvanometer is a galvanometer specially designed to measure the quantity of charge displaced in current for a short duration such as charging and discharging of capacitor.

---> moving part  has high moment of inertia.
---> it has long period of variation.

Principle of working Of ballistic galvanometer:
when a current passes through a coil of a Ballistic galvanometer then it rotates in magnetic field and the deflection of coil is proportional to the quantity of charge passing through it.

Where as ;

Spot galvanometer is known as reflecting galvanometer.
A galvanometer having a small mirror attached to the moving element .It measures extremely small currents.