Physics Test 28

Total Questions: 25

1 - Which one of the following is not an advantage of three phase system of electric power supply over one phase system?

A ) The output voltage is higher ✅
B ) The power consumption is less
C ) The total output is almost constant
D ) The output of a 3-phase machine is greater than that of a single phase machine

2 - Ball bearing are used to reduce friction by:

A ) Applying lubricants to the balls used
B ) Reducing the area of contact with the use of metallic balls ✅
C ) Increasing the ara of contact with the use of metallic balls
D ) None of these

3 - An electric motor runs on which principle?

A ) Electrical energy can be converted into chemical energy in the presence of magnetic fields
B ) A conductor carrying current in the direction perpendicular to the external magnetic field feels a force ✅
C ) The current flowing through a conductor causes generation of heat that drives the engine
D ) Changing magnetic field induces an electromotive force in a conductor

4 - Which of the following functions is performed by a photo cell?

A ) It converts chemical energy into electrical energy
B ) It converts magnetic energy into electrical energy
C ) It converts light energy into electrical energy ✅
D ) It converts electrical energy into light energy

5 - Electronics is the study of

A ) Flow of molecules ✅
B ) Flow of electrons
C ) Flow of photons
D ) All are true

6 - A car and a loaded truck are moving with the same speed along a road. As compared to the truck,the car shall posses

A ) More kinetic energy
B ) More potential energy
C ) Less kinetic energy ✅
D ) More mechanical energy

7 - When a moving bus stops suddenly,the passengers are pushed forward because of the

A ) Friction between the earth and the bus
B ) Friction between the passengers and the earth
C ) Inertia of the passengers ✅
D ) Inertia of the bus

8 - Erect and virtual images are always produced by

A ) Plane and convex mirrors ✅
B ) Plane mirrors alone.
C ) Concave and convex mirrors.
D ) Concave mirrors alone.

9 - The working of the receiver of a telephone depends upon the

A ) Change in magnetization of an electromagnet, which causes a diaphragm to vibrate.
B ) Efficiency of the loudspeaker which enhances the loudness of sound
C ) Conversion of electric signal, after its amplification into sound wave
D ) Diaphragm which is made to vibrate by the incoming sound wave ✅

11 - The hydraulic brakes used in automobiles is a direct application of:

A ) Archimedes principle
B ) Toricellian law
C ) Bernoulli's theorem
D ) Pascal's law ✅

12 - In T. V. transmission:

A ) Sound and video signals are transmitted simultaneously ✅
B ) Sound is transmitted first and then the video signal follows
C ) Video signal is transmitted first, followed by sound signal
D ) Sound and video signals are transmitted from different places at the same time

13 - Surface tension in a liquid is due to

A ) Adhesive force between the molecules
B ) Cohesive force between the molecules ✅
C ) Gravitational force between the molecules
D ) Electrical force between the molecules

14 - Springs of shock absorbers of automobiles and railway coaches are made of steel and not of rubber because steel is

A ) More durable than rubber
B ) Less expensive than rubber in the long run
C ) Less elastic than rubber
D ) More elastic than rubber ✅

15 - Why does the mercury column in the barometer fall rapidly before a severe storm?

A ) It is due to decrease in humidity in air
B ) It is due to the rise in atmospheric pressure
C ) It is due to the fall in atmospheric pressure ✅
D ) It is due to the severe heat energy from the sun

16 - Why does water boil below 100°C at higher altitudes?

A ) There is lesser dissipation of heat at higher altitudes
B ) Water available at higher altitudes is purer than that in the plains
C ) Pollution -free air at higher altitudes increases the calorific value of fuel used
D ) The atmospheric pressure at higher altitudes is low as compared to that at sea level ✅

18 - Echo is the effect produced due to

A ) Absorption of sound
B ) Dispersion of sound
C ) Reflection of sound ✅
D ) Refraction of sound

19 - In a photographic camera fitted with a convex lens, which of the following types of images will be formed on the film?

A ) Eract and real
B ) Inverted and real ✅
C ) Imaginary and erect
D ) The type of image formed will depend on the distance between the lens and the object

20 - In the modern-day computers,when operational,the electrical impulses travel

A ) At the speed of sound
B ) At seven times the speed of sound
C ) At half the speed of light
D ) Nearly at speed of light ✅

22 - Why are shields made of iron usually provided around precision instruments?

A ) For protection against the effect of external magnetic fields ✅
B ) For guarding the instruments against unauthorised handling
C ) For protection against the effect of moisture in the air
D ) For absorbing heat generated during the functioning of the instrument

23 - Why are transformers used in the transmission of electric power?

A ) Because they speed up transmission
B ) Because they can conserve electrical energy
C ) Because they can reduce transmission losses ✅
D ) Because they can help to distribute electrical energy efficiently

24 - A mixture of which of the following gases is used in the manufacture of electric bulbs?

A ) Nitrogen and Argon
B ) Nitrogen and Oxygen
C ) Oxygen and Argon ✅
D ) Oxygen and Hydrogen

25 - A fresh egg skins in pure water,whereas it floats in saturated salty water. This is due to

A ) Higher density of the salty water ✅
B ) Higher density of the pure water
C ) The fluid matter inside the egg-shell
D ) The fact that the egg-shell is made of calcium which is heavier than pure water