Electric Charges and Fields — Physics STD 12 Science — Question

Which one statement is correct ? A parallel plate air condenser is connected with a battery. Its charge, potential, electric field and energy are  and respectively. In order to fill the complete space between the plates a dielectric slab is inserted, the battery is still connected. Now the corresponding values Q, V, E  and U are in relation with the initially stated as 

(a) Q >

(b)

(c) V >

(d)

A radioactive isotope X with a half-life of 1.37   years decays to Y which is stable. A sample of rock from the moon was found to contain both the elements X and Y which were in the ratio of 1 : 7. The age of the rock is

(a) 1.96  years

(b) 3.85  years

(c) 4.11  years

(d) 9.59  years

Which of the following is a wrong description of binding energy of a nucleus?

1. It is the energy required to break a nucleus into its constituent nucleons.
2. It is the energy made available when free nucleons combine to form a nucleus.
3. It is the sum of the rest mass energies of its nucleons minus the rest mass energy of the nucleus.
4. It is the sum of the kinetic energy of all the nucleons in the nucleus.

Curie-Weiss law is obeyed by iron at a temperature ......

(a) Below Curie temperature	(b) Above Curie temperature
(c) At Curie temperature only	(d) At all temperatures

A circular loop has a radius of 5 cm and it is carrying a current of 0.1 amp. Its magnetic moment is

(a) 1.32	(b) 2.62
(c) 5.25	(d) 7.85

A presbyopic patient has near point as 30 cm and far point as 40 cm. The dioptric power for the corrective lens for seeing distant objects is

(a) 40 D

(b)  4 D

(c)   – 2.5 D

(d)  0.25 D

The activity of a radioactive sample

(a) Can be increased by heating it	(b) Is independent of physical parameter
(c) Cannot be increased by any method	(d) Both (b) and (c)

The radius of curvature of the path of the charged particle in a uniform magnetic field is directly proportional to

(a) The charge on the particle	(b) The momentum of the particle
(c) The energy of the particle	(d) The intensity of the field

Which radiation in sunlight, causes heating effect

(a) Ultraviolet

(b) Infrared

(c) Visible light

(d) All of these

The coefficient of mutual inductance of the two coils is 5H. The current through the primary coil is reduced to zero value from 3A in 1millisecond. The induced emf in the secondary coils is.