Magnetism and Matter — Physics STD 12 Science — Question

A circular loop carrying a current is replaced by ann equivalent magnetic dipole. A point on the axis of the loop is in:

1. End-on position.
2. Broadside-on position.
3. Both.
4. None.

A free neutron decays to a proton but a free proton does not decay to a neutron. This is because:

The area of a coil is 500cm² and the number of turns in it is 2000. It is kept perpendicular to a magnetic field of induction 4 × 10-5Wb/ m². The coil is rotated through 180 in 0.1 second. If the resistance of the total circuit is 20Ω, then the value of the induced charge flowing in the circuit will be :

A conducting disc of radius r spins about its axis with an angular velocity ω. There is a uniform magnetic field of magnetude B perpendicular to the plane of the disc. C is the centre of the ring.

A steady current is passing through a linear conductor of non uniform cross-section. The net quantity of charge crossing any cross section per second is:

When a wire loop is rotated in a magnetic field, the direction of induced e.m.f. changes once in each

(a)  revolution

(b)  revolution

(c) 1 revolution

(d) 2 revolution

A semiconducting device is connected in a series circuit with a battery and a resistance. A current is found to pass through the circuit. If the polarity of the battery is reversed, the current drops to almost zero. the device may be:

1. An intrinsic semiconductor.
2. A p-type semiconductor.
3. An n-type semiconductor.
4. A p-n junction.

The electric field due to a dipole at a distance r  on its axis is

(a) Directly proportional to	(b) Inversely proportional to
(c) Directly proportional to	(d) Inversely proportional to

A parallel plate capacitor of plate separation 2 mm is connected in an electric circuit having source voltage 400 V. if the plate area is 60 cm², then the value of displacement current for   will be

(a) 1.062 amp

(b) 1.062  amp

(c) 1.062  amp

(d) 1.062  amp