MODEL PAPER 1 — Physics STD 12 Science — Question

The coils of a step down transformer have 500 and 5000 turns. In the primary coil an ac of 4 ampere at 2200 volts is sent. The value of the current and potential difference in the secondary coil will be

(a) 20 A, 220 V

(b) 0.4 A, 22000 V

(c) 40 A, 220 V

(d) 40 A, 22000 V

Which decay increases the atomic number?

Magnetic field due to a ring having n turns at a distance x on its axis is proportional to (if r = radius of ring)

(a)

(b)

(c)

(d)

Which of the following quantities do not depend on the choice of zero potential or zero potential energy?

The potential gradient along the length of a uniform wire is 10 volt/metre.  B and C are the two points at 30 cm  and  60 cm point on a meter scale fitted along the wire. The potential difference between B  and  C will be

(a) 3 volt

(b) 0.4 volt

(c) 7 volt

(d) 4 volt

A heating coil is labelled 100 W, 220 V. The coil is cut in half and the two pieces are joined in parallel to the same source. The energy now liberated per second is

(a) 200 J

(b) 400 J

(c) 25 J

(d) 50 J

A coil is wound as a transformer of rectangular cross-section. If all the linear dimensions of the transformer are increased by a factor 2 and the number of turns per unit length of the coil remain the same, the self  inductance increased by a factor of

(a)  16

(b) 12

(c)  8

(d) 4

A dip needle in a plane perpendicular to magnetic meridian will remain

(a) Vertical	(b) Horizontal
(c) In any direction	(d)  At an angle of dip to the horizontal

The magnitude of the earth’s magnetic field at a place is  and the angle of dip is δ. A horizontal conductor of length l lying along the magnetic north-south moves eastwards with a velocity v. The emf induced across the conductor is

(a) Zero

(b)

(c)

(d)