Electrostatic Potential and Capacitance — Physics STD 12 Science — Question

Threshold frequency of which of the following metal does not lie in the ultraviolet region. (In case of photoelectric effect)

Which of the following plots may represent the thermal energy produced in a resistor in a given time as a function of the electric current

(a) a

(b) b

(c) c

(d) d

In an AC generator, a coil with N turns, all of the same area A and total resistance R, rotates with frequency 1rad/ s in a magnetic field B. The maximum value of emf generated in the coil is:

A star which appears blue will be

(a) As hot as the sun	(b) Cooler than the sun
(c) Very cold indeed	(d) Much hotter than the sun

The relationship between λ and half life ( of a radioactive substance is

(a) λ =

(b)  λ =

(c) λ =

(d)  λ =

When a PN junction diode is reverse biased

(a) Electrons and holes are attracted towards each other and move towards the depletion region

(b) Electrons and holes move away from the junction depletion region

(c) Height of the potential barrier decreases

(d) No change in the current takes place

If yellow light in the Young's double slit experiment is replaced by red light, the fringe width will

(a) Decrease	(b) Remain unaffected
(c) Increase	(d) First increase and then decrease

In a fission reaction , the binding energy per nucleon of X and Y is 8.5 MeV whereas of  is 7.6 MeV. The total energy liberated will be about

(a) 200 KeV

(b) 2 MeV

(c) 200 MeV

(d) 2000 MeV

Which of the following is wrong statement about binding energy?

Two similar plano-convex lenses are combined together in three different ways as shown in the adjoining figure. The ratio of the focal lengths in three cases will be

(a) 2 : 2 : 1

(b) 1 : 1 : 1

(c) 1 : 2 : 2

(d) 2 : 1 : 1