Magnetism And Matter — Physics STD 12 Science — Question

In a transformer, number of turns in the primary are 140 and that in the secondary are 280. If current in primary is 4A then that in the secondary is

(a) 4 A

(b) 2 A

(c) 6 A

(d) 10 A

The self inductance of a straight conductor is.

Energy stored in a coil of self inductance 40mH carrying a steady current of 2 A is

(a) 0.8 J

(b) 8 J

(c) 0.08 J

(d) 80 J

A long horizontal metallic rod with length along the east-west direction is falling under gravity. The potential difference between its two ends will           

(a) Be zero

(b) Be constant

(c) Increase with time

(d) Decrease with time

In the above question, potential difference across the 40Ω resistance will be

(a) Zero

(b) 80 V

(c) 40 V

(d) 120 V

A convex lens of focal length 12 cm is made of glass of μ = . What will be its focal length when immersed in liquid of μ =  

(a) 6 cm

(b) 12 cm

(c) 24 cm

(d) 30 cm

Suppose the medium in the previous question is water. Select the correct option(s) from the list given in that question.

A wire carrying current i is shaped as shown. Section AB is a quarter circle of radius r.  The magnetic field is directed

(a) At an angle π/4  to the plane of the paper

(b) Perpendicular to the plane of the paper and directed in to the paper

(c) Along the bisector of the angle ACB  towards AB

(d) Along the bisector of the angle ACB away from AB

In Millikan's oil drop experiment an oil drop carrying a charge Q is held stationary by a potential difference 2400 V  between the plates. To keep a drop of half the radius stationary the potential difference had to be made 600 V. What is the charge on the second drop

(a)

(b)

(c) Q

(d)

An ammeter and a voltmeter of resistance R are connected in series to an electric cell of negligible internal resistance. Their readings are A and V respectively.  If another resistance R is connected in parallel with the voltmeter

(a) Both A and V will increase	(b) Both A and V will decrease
(c) A will decrease and V will increase	(d) A will increase and V will decrease