Class 8 physics MCQ based on energy,light & heat for 2nd term exam

 1.select the correct alternative:

1.1 In boiling:

A. All molecules of liquid begin to escape out.

B. Only the molecules at the surface escape out.

C. The temperature of liquid Rises by absorbing heat from surrounding.

D. The molecules get attracted within the liquid.

1.2 the rate of evaporation of a liquid decreases when:

A. Temperature of liquid increases

B. Liquid sport in a vessel of large surface area

C. Air is not blown above the surface of liquid

D. Humidity increases.

1.3 two rods A and B of the same metal but of length 10 m and 2 m respectively are heated from 0 degree Celsius to 100 degree Celsius.then:

A. Both the rods A and B elongate the same

B. The rod A elongates more than the rod B.

C. The rod B elongates more than the rod A.

D. The rod A elongates,but the rod B contracts.

1.4 a given volume of alcohol and the same volume of water are heated from the room temperature to the same temperature then

A. Alcohol contracts but water expands

B. Water contracts but alcohol expands

C. Alcohol expands more than water

D. Water expands more than alcohol.

1.5 the SI unit of coefficient of cubical expansion is

A.°C‐¹

B.°C-²

C.°C-³

D.°C‐⁰

1.6 the angle between the incident ray and the refracted ray is called

A. Angle of deviation

B. Angle of incidence

C. Angle of refraction

D. Angle of emergence

1.7 if the radius of curvature of a convex mirror is 40 cm, it's focal length is

A. 10 cm

B 20cm

C.30cm

D.40cm

1.8 the image formed by a concave mirror is

A. Erect and diminished

B. Erect and enlarged

C.erect and same size.

D. Inverted and enlarged.

1.9 a girl lift a luggage from height 1 m to 2 m the potential energy will become

A.half

B.double

C. One-third

D.one-fourth

1.10 no work is done by a force if the body

A. Moves in opposite direction

B. Moves in the direction of force

C. Does not move

D. None of these.

1.11 the SI unit of work is

A. Second

B. Metre

C. Newton

D. Newton metre

1.12 when a body reduces his mass by 50% then his potential energy becomes

A.Half

B.double

C. Four times

D.no change

1.13 concave mirror is used

A. As a rear view mirror by a driver

B. As saving mirror

C. As a reflector in street light

D. None of these.

1.14 the image formed by a concave mirror is of the same size as the object if the object is placed

A. At Focus

B. At C

C. Between the pole and the focus

D. Between the focus and the centre of curvature

1.15 A Ray of light moving from an optically denser medium to a rarer medium

A. Bends away from the normal

B. Bends toward's the normal

C. Remains undeviated

D. None of the above.

2.