Question

how does the galvanometer respond when the switch is closed in the primary coil?

Answer 1

when switch in primary is closed generally current will build up and the pointer will deflect either in right or left direction

Answer 2

Yup as say above, When switch is closed in primary coil, galvanometer shows deflection either in Right or Left.

Answer 3

why is that ? @sidsiddhartha

Answer 4

Galvanometer is the device which is used to "detect" the current in a circuit. when current flows through the circuit, it shows the deflection.