Alternating Current — Physics STD 12 Science — Question

Four plates of the same area of cross-section are joined as shown in the figure. The distance between each plate is d. The equivalent capacity across A and B will be

(a)

(b)

(c)

(d)

A beam of parallel rays is brought to a focus by a plano-convex lens. A thin concave lens of the same focal length is joined to the first lens. The effect of this is

(a) The focal point shifts away from the lens by a small distance

(b) The focus remains undisturbed

(c) The focus shifts to infinity

(d) The focal point shifts towards the lens by a small distance

A charge Q is divided into two parts of q  and Q - q. If the coulomb repulsion between them when they are separated is to be maximum, the ratio of   should be

(a) 2

(b) 1/2

(c) 4

(d) 1/4

A series R-C circuit is connected to an alternating voltage source. Consider two situation:
(a) When capacitor is filled
(b) When capacitor is mica filled
Current through resister is i and voltage across capacitor is V then:

The total charge induced in a conducting loop when it is moved in magnetic field depends on

(a) The rate of change of magnetic flux	(b) Initial magnetic flux only
(c) The total change in magnetic flux	(d) Final magnetic flux only

The molecules in which centres of positive and negative charges are separated are called as:

A man with defective eyes cannot see distinctly object at the distance more than 60 cm from his eyes. The power of the lens to be used will be

(a) + 60 D

(b) – 60 D

(c) – 1.66 D

(d)

Three bulbs of 40W, 60W and 100W are arranged in series with 220V. Which bulb has minimum resistance

(a) 40W

(b) 60W

(c) 100W

(d) Equal in all bulbs

In beta decay

(a) The parent and daughter nuclei have same number of protons

(b) The daughter nucleus has one proton less than the parent nucleus

(c) The daughter nucleus has one proton more than the parent nucleus

(d) The daughter nucleus has one neutron more than the parent nucleus

The forbidden energy gap for germanium crystal at 0 K is: