A galvanometer has a coil of resistance 100 ohm and gives a full scale deflection for 30 mA current. If it is to work as a voltmeter of 30 volt range, the resistance required to be added will be

A square current carrying loop is suspended in a uniform magnetic field acting in the plane of the loop. If the force on one arm of the loop is the net force on the remaining three arms of the loop is

Charge q is uniformly spread on a thin ring of radius R. The ring rotates about its axis with a uniform frequency $$f$$ Hz. The magnitude of magnetic induction at the center of the ring is

A galvanometer havings a coil resistance of 60 $$\Omega $$ shows full scale deflection when a current of 1.0 amp passes through it. It can be converted into an ammeter to read currents upto 5.0 amp by