Assertion (A) : Diamagnetic substances exhibit magnetism.

Reason (R) : Diamagnetic materials do not have permanent magnetic dipole moment.

Assertion (A) : Work done in moving a charge around a closed path, in an electric field is always zero.

Reason (R) : Electrostatic force is a conservative force.

Assertion (A) : In Young's double slit experiment all fringes are of equal width.

Reason (R) : The fringe width depends upon wavelength of light $$(\lambda)$$ used, distance of screen from plane of slits (D) and slits separation (d).

Briefly explain why and how a galvanometer is converted into an ammeter.