A sensitive magnetic instrument can be shielded very effectively from outside magnetic fields by placing it inside a box of

Why magnetic field exist inside a magnet?

The magnetic field lines inside a bar magnet

The magnetic field lines inside a bar magnet

The magnetic field inside a solenoid is

The magnetic field inside a solenoid is

The magnetic field inside a solenoid is

Assertion : Any instrument can be protected from external magnetic field by putting inside a wooden box. Reason : Iron is a magnetic substance.