Magnetism And Matter — Physics STD 12 Science — Question

Three equal chares + q each are placed at the three vertices of an equilateral triangle. The electric field at the centroid of the triangle is ___________ .

A beam of monochromatic blue light of wavelength 4200Å in air travels in water (μ = 4/3). Its wavelength in water will be

(a) 2800 Å

(b) 5600 Å

(c) 3150 Å

(d) 4000 Å

The magnet can be completely demagnetized by

(a) Breaking the magnet into small pieces

(b) Heating it slightly

(c) Droping it into ice cold water

(d) A reverse field of appropriate strength

A physicist works in a laboratory where the magnetic field is 2 T. She wears a necklace enclosing area 0.01 m² in such a way that the plane of the necklace is normal to the field and is having a resistance R = 0.01 Ω. Because of power failure, the field decays to 1 T in time 10^–3 seconds. Then what is the total heat produced in her necklace ? (T = Tesla)

(a) 10 J

(b) 20 J

(c) 30 J

(d) 40 J

Material A has critical angle   and material B has critical angle . Then which of the following is true

(i) Light can be totally internally reflected when it passes from B to A

(ii) Light can be totally internally reflected when it passes from A to B

(iii) Critical angle for total internal reflection is  

(iv) Critical angle between A and B is

(a) (i) and (iii)

(b) (i) and (iv)

(c) (ii) and (iii)

(d) (ii) and (iv)

When a potential difference V is applied across a conductor at a temperature T, the drift velocity of electrons is proportional to:

In a photon-particle collision, the quantity that does not remain conserved is:

A pendulum clock keeping correct time is taken to high altitudes:

1. It will keep correct time.
2. Its length should be increased to keep correct time.
3. Its length should be decreased to keep correct time.
4. It cannot keep correct time even if the length is changed.

When light is refracted, which of the following does not change?

Two non-ideal identical batteries are connected in parallel. Consider the following statements      

(i) The equivalent e.m.f. is smaller than either of the two e.m.f.s

(ii) The equivalent internal resistance is smaller than either of the two internal resistances

(a) Both (i) and (ii) are correct	(b) (i) is correct but (ii) is wrong
(c) (ii) is correct but (i) is wrong	(d) Both (i) and (ii) are wrong