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

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