Moving Charges and Magnetism — Physics STD 12 Science — Question

A ferromagnetic material is placed in an external magnetic field. The magnetic domains:

Taking Rydberg’s constant  first and second wavelength of Balmer series in hydrogen spectrum is

(a) 2000 Å, 3000 Å

(b) 1575 Å, 2960 Å

(c) 6529 Å, 4280 Å

(d) 6552 Å, 4863 Å

What is the nature of equipotential surfaces in case of a positive point charge?

A transformer has turn ratio 100/1. If secondary coil has 4 amp current then current in primary coil is

(a) 4 A

(b) 0.04 A

(c) 0.4 A

(d) 400 A

If one starts with one curie of radioactive substance (T_1/2 = 12 hrs) the activity left after a period of 1 week will be about

(a) 1 curie

(b) 120 micro curie

(c) 60 micro curie

(d) 8 mili curie

The nature of effective nuclear forces is :

The radius of two metallic spheres A and B  are  and  respectively (. They are connected by a thin wire and the system is given a certain charge. The charge will be greater

(a) On the surface of the sphere B	(b) On the surface of the sphere  A
(c) Equal on both	(d) Zero on both

A radio transmitter operates at a frequency of 880 kHz and a power of 10 kW. The number of photons emitted per second are

(a) 1.72

(b) 1327

(c) 13.27

(d) 0.075

The impact of an image on the retina remains for

(a) 0.1 sec

(b)  0.5 sec

(c) 10 sec

(d)  15 sec