Electric Charges and Fields — Physics STD 12 Science — Question

If two soap bubbles of different radii are connected by a tube:

1. Air flows from bigger bubble to the smaller bubble till the sizes become equal.
2. Air flows from bigger bubble to the smaller bubble till the sizes are interchanged.
3. Air flows from the smaller bubble to the bigger.
4. There lis no flow of air.

Mark the correct statements about the friction between two bodies:

1. Static friction is always greater than the kinetic friction.
2. Coefficient of static friction is always greater than the coefficient of kinetic friction.
3. Limiting friction is always greater than the kinetic friction.
4. Limiting friction is never less than static friction.

A prism having an apex angle 4^o and refraction index 1.5 is located in front of a vertical plane mirror as shown in figure. Through what total angle is the ray deviated after reflection from the mirror

(a) 176o

(b) 4o

(c) 178o

(d) 2o

A solid is completely immersed in a liquid. The force exerted by the liquid on the solid will.

1. Increase if it is pushed deeper inside the liquid.
2. Change if its orientation is changed.
3. Decrease if it is taken partially out bf the liquid.
4. Be in the vertically upward direction.

The speed of electromagnetic wave in vacuum depends upon the source of radiation

(a) Increases as we move from g-rays to radio waves

(b) Decreases as we move from g-rays to radio waves

(c) Is same for all of them

(d) None of these

The strength of the magnetic field in which the magnet of a vibration magnetometer is oscillating is increased 4 times its original value. The frequency of oscillation would then become

(a) Twice its original value	(b) Four times its original value
(c) Half its original value	(d) One-fourth its original value

When a beam of light is used to determine the position of an object, the maximum accuracy is achieved if the light is

(a) Polarised	(b) Of longer wavelength
(c) Of shorter wavelength	(d) Of high intensity

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

1. The equivalent emf is smaller than either of the two emfs.
2. The equivalent internal resistance is smaller than either of the two internal resistances.

1. Both A and B are correct.
2. A is correct but B is wrong.
3. B is correct but A is wrong.
4. Both A and B are wrong.

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)

The energy gap in a conductor at room temperature is ________ .