Electric Charges and Fields — Physics STD 12 Science — Question

A circular coil of radius R carries an electric current. The magnetic field due to the coil at a point on the axis of the coil located at a distance r from the centre of the coil, such that r >> R, varies as

(a)

(b)

(c)

(d)

A solenoid of length 0.5 m has a radius of 1 cm and is made up of 1000 turns. It carries a current of 5 A . The magnitude of the magnetic field inside the solenoid is ________ T.

A short magnet of moment 6.75 Am² produces a neutral point on its axis. If horizontal component of earth's magnetic field is 5  , then the distance of the neutral point should be

(a) 10 cm

(b) 20 cm

(c) 30 cm

(d) 40 cm

The Bohr model of atoms            

(a) Assumes that the angular momentum of electrons is quantized

(b) Uses Einstein’s photo-electric equation

(c) Predicts continuous emission spectra for atoms

(d) Predicts the same emission spectra for all types of atoms

The capacity of the parallel plate capacitor increases when:

A  cut diamond sparkles because of its

(a) Hardness	(b) High refractive index
(c) Emission of light by the diamond	(d) Absorption of light by the diamond

In the circuit shown here, E₁ = E₂ = E₃ = 2 V and R₁ = R₂ = 4 ohms.  The current flowing between points A and B through battery E₂ is

(a) Zero	(b) 2 amp from A to B
(c) 2 amp from B to A	(d) None of the above

Water enters through end A with a speed v₁ and leaves through end B with a speed v₂ of a cylindrical tube AB. The tube is always completely filled with water. In case I the tube is horizontal, in case II it is vertical with the end A upward and in case III it is vertical with the end B upward. We have v₁ = v₂ for

1. Case I.
2. Case II.
3. Case III.
4. Each case.