Atoms — Physics STD 12 Science — Question

A strip of copper and another of germanium are cooled from room temperature to 80K. The resistance of:

p-n junction diode acts as:

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)

When electromagnetic waves enter the ionised layer of ionosphere, then the relative permittivity i.e. dielectric constant of the ionised layer:

Electric field strength due to a point charge of 5μC  at a distance of 80 cm from the charge is

(a)  N/C

(b) 7N/C

(c)  5N/Cv

(d) 4N/C

Identify the correct statement about the magnetic field lines:

A positively charged particle moving in east direction enters a region of uniform magnetic field directed vertically upwards. What will be the path of the particle?

Which of the following is wrong for interference fringes?

A plane electromagnetic wave is incident on a material surface. If the wave delivers momentum p and energy E, then

(a) p = 0, E = 0

(b) p ¹ 0, E ¹ 0

(c) p ¹ 0, E = 0

(d) p = 0, E ¹ 0

Which of the following is diamagnetism

(a) Aluminium

(b) Quartz

(c) Nickel

(d) Bismuth