Physics Questions and Answers

  • 1. Two electric bulbs marked 25W – 220V and 100W – 220V are connected in series to a 440Vsupply. Which of the bulbs will fuse?
   A.) 100 W
   B.) 25 W
   C.) Both
   D.) Neither

Answer: Option 'B'

Resistances of both the bulbs are

R1=V^2/P1 = 220^2/25

R2 = V^2/P2 = 220^2/100

Hence  R1gt ; R2R1gt ; R2

When connected in series, the voltages divide in them in the ratio of their resistances. The voltage of 440 V devides in such a way that voltage across 25 w bulb will be more than 220 V. Hence 25 w bulb will fuse.

  • 2. It is more difficult to walk on ice than on a concrete road because
   A.) there is more friction between the ice and feer
   B.) there is very little friction between the ice and feet pressing it
   C.) ice is soft when compared to concrete
   D.) None of these

Answer: Option 'B'

It is the friction between the feet and the ground that helps us to walk. Without this friction we would slip and fall

  • 3. Which of the following is not a vector quantity
   A.) speed
   B.) velocity
   C.) torque
   D.) displacement

Answer: Option 'A'

speed

  • 4. The working principle of a washing machine is
   A.) centrifugation
   B.) diffusion
   C.) reverse osmosis
   D.) dialysis

Answer: Option 'A'

centrifugation

  • 5. Nuclear sizes are expressed in a unit named
   A.) Newton
   B.) Fermi
   C.) Angstrom
   D.) Tesla

Answer: Option 'B'

Nuclear sizes are expressed in a unit called "Fermi" which is a unit of length equal to 10−15 metre (one femtometre), used in nuclear physics. It is similar to the diameter of a proton.

  • 6. The speed of light will be minimum while passing through
   A.) air
   B.) water
   C.) vaccum
   D.) glass

Answer: Option 'D'

glass

  • 7. It is more difficult to walk on ice than on a concrete road because 
   A.) there is very little friction between the ice and feet pressing it
   B.) ice is soft when compared to concrete
   C.) there is more friction between the ice and feer
   D.) None of these

Answer: Option 'A'

there is very little friction between the ice and feet pressing it

  • 8. A solid ball of metal has a spherical cavity inside it. When the ball is heated the volume of the cavity will
   A.) remain unaffected
   B.) increase
   C.) decrease
   D.) have its shape changed

Answer: Option 'B'

The metal ball can be considered  to be made up of several layers of thinner ones. On heating each of these layers will increase in radius. As the inner most layer also increases its radius, the volume inside it i.e, the volume of the hollow portion will also increase.

  • 9. If a sound travels from air to water, the quantity that remain unchanged is
   A.) wavelength
   B.) velocity
   C.) amplitude
   D.) frequency

Answer: Option 'D'

frequency

  • 10. When a bottle of perfume is opened in one corner of a room the smell spreads soon throughout the room. This is an example of
   A.) viscosity
   B.) diffusion
   C.) capillarity
   D.) surface tension

Answer: Option 'B'

diffusion
Diffusion is the spreading  - mixing of gases through molecular motion.

  • 11. The core of an electromagnet is made of soft iron because soft iron has 
   A.) large density and large retentivity
   B.) small susceptibility and small retentivity
   C.) large susceptibility and small retentivity
   D.) small density and large retentivity

Answer: Option 'C'

large susceptibility and small retentivity

  • 12. Skating on ice is possible because 
   A.) the pressure on the ice due to skate melts the ice by lowering its melting point forming a thin film of water
   B.) the pressure on the ice due to skate raises its melting point
   C.) the surface of ice is smooth
   D.) ice is cold

Answer: Option 'A'

the pressure on the ice due to skate melts the ice by lowering its melting point forming a thin film of water
Here is a case of  lowering of melting point of ice with increase of pres

  • 13. The basic reason for the extraordinary sparkle of suitably cut diamond is that
   A.) it has well defined cleavage planes
   B.) it has a very high transparency
   C.) it has a very high refractive index
   D.) it is very hard

Answer: Option 'C'

it has a very high refractive index

  • 14. Which of the following is not the unit of time
   A.) Leap year
   B.) Parallactic second
   C.) Micro Second
   D.) Solar day

Answer: Option 'B'

Parallactic second

  • 15. Temperature can be expressed as derived quantity in terms of any of the following
   A.) length,mass and time
   B.) length and mass
   C.) mass and time
   D.) in terms of none

Answer: Option 'D'

in terms of none

  • 16. The minimum number of Non zero non collinear vectors required to produce a zero vector is
   A.) 1
   B.) 2
   C.) 3
   D.) 4

Answer: Option 'C'

3

  • 17. The base of an electric iron is brightly polished mainly
   A.) to reduce heat loss by radiation
   B.) to make it more durable
   C.) to make it smooth and frictionless
   D.) to make it rust-proof

Answer: Option 'A'

Polished surfaces are poor radiators of heat. So loss of heat on that account is reduced and the electric iron remains hotter than otherwise.

  • 18. What is the SI unit of pressure
   A.) Pascal
   B.) Dyne
   C.) Newton
   D.) Jule

Answer: Option 'A'

Pascal

  • 19. Formation of shadows can be explained by 
   A.) rectilinear propagation of light
   B.) reflection
   C.) refraction
   D.) total internal reflection

Answer: Option 'A'

In this position, the head light will be at the principal focus so that the rays of light falling on the cancave mirror will be rendered parallel

  • 20. A bucket of water is hung from a spring balance. A piece of iron is suspended in the water without touching the sides or touching the bottom of the bucket. The reading of the spring balance
   A.) does not change
   B.) will increase
   C.) will decrease
   D.) varies with the increase of depth of the immersion of the iron piece

Answer: Option 'B'

will increase
When the piece of iron is lowered into the water, the water level in the bucket increases. And so the pressure at the bottom of bucket also increases. Thus the total thrust at the botto also increases. Therefore the spring balance reading increases.

  • 21. Pieces of camphor placed on water move about rapidly. This is because of
   A.) diffusion
   B.) viscosity
   C.) surface tension
   D.) capillarity

Answer: Option 'C'

The Camphor slowly dissolves in the water lowering the latter's surface tension in the immediate neighbourhood. The stronger pull exerted by the uncontaminated portion of water brings about a movement of the surface and the camphor particles are carried along with it. When after sometime the whole surface settles for the reduced tension, the movement of the camphor too short.

  • 22. An air bubble in water will act like a
   A.) convex lens
   B.) concave lens
   C.) convex mirror
   D.) concave mirror

Answer: Option 'B'

concave lens

  • 23. Ultrasonic waves are used for stirring liquid solutions because they 
   A.) can produce perfectly homogeneous solutions
   B.) do not produce noise during the operation
   C.) are easy to produce
   D.) do not produce chemical reactions in the solution

Answer: Option 'A'

can produce perfectly homogeneous solutions

  • 24. Masses of stars and galaxies are usually expressed in terms of
   A.) solar mass
   B.) neutron mass
   C.) earth's mass
   D.) lunar mass

Answer: Option 'A'

solar mass

  • 25. Ball bearings are used in cycles, scooters etc to
   A.) Increase the friction between the wheel and the axle
   B.) Reduce the friction between the wheel and the axle
   C.) Reduce the friction between ground and the whee
   D.) None of the above

Answer: Option 'B'

Reduce the friction between the wheel and the axle

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