Physics Test 30

Total Questions: 25

3 - What are ultrasonic waves?

A ) Sound waves having frequency shorter than audio -frequency range
B ) Sound waves produced in a vacuum
C ) Sound waves having frequency higher than audio-frequency range ✅
D ) None of these

4 - In the process of galvanization an iron sheet is coated with:

A ) Aluminum
B ) Zinc ✅
C ) Tin
D ) Galena

5 - A radar which detects the presence of an enemy aircraft uses

A ) Sound waves
B ) Radiowaves ✅
C ) Electric waves
D ) Ultrasonic waves

6 - Fish plates are used in railway tracks

A ) To avoid tracks being distorted due to temperature fluctuation
B ) To control speed of the train ✅
C ) To connect two rails
D ) To keep the rails equidistant

7 - Food is cooked quickly in a pressure cooker because

A ) Boiling point of water is decreased
B ) Boiling point of water is increased ✅
C ) It absorbs heat quickly
D ) It retains heat for a long duration

8 - A fuse wire is used to

A ) To make the electrical circuit strong
B ) Convert AC inDC
C ) Convert DC into AC
D ) Prevent an unduly high electric current to pass through a circuit ✅

9 - A molecule is

A ) A class of organic compounds
B ) The smallest unit of a substance that retains the properties of the substance ✅
C ) The spectrum of a substance
D ) A small mass

10 - The nucleus of an atom consists of

A ) Protons+Electrons
B ) Only proton
C ) Proton+Neutron+Electron
D ) Protons+neutrons ✅

12 - Sound travels with a different speed in different media. In what order does the velocity of sound increase in these media?

A ) Water, iron and air
B ) Iron, air and water
C ) Air,water and iron ✅
D ) Iron, water and air

13 - In electric fittings, the wires are earthed because

A ) In case of a short circuit, current passes to the earth ✅
B ) It avoids leakage of electricity
C ) It completes the electric circuit
D ) It reduces fluctuation

14 - Which of the following metals is used in aircraft?

A ) Chromium
B ) Titanium
C ) Palladium ✅
D ) None of these

15 - During rusting

A ) Iron gains weight ✅
B ) Iron loses weight
C ) Weight of iron remains unchanged
D ) Iron volatilizes

16 - When water boils, its temperature

A ) Begins to increase
B ) Begins to decrease
C ) Remains constant ✅
D ) Fluctuates

17 - Rectifiers are used to convert

A ) DC to AC
B ) AC to DC ✅
C ) High voltage to low voltage
D ) Low voltage to high voltage

19 - Which one of the following statements is correct? A slab of ice kept in a room:

A ) Does not radiate heat
B ) Does not radiate heat but absorbs heat from the sorrounding ✅
C ) Radiates heat but absorbs more heat from the sorrounding
D ) Radiates heat more than that absorbed by it from the sorrounding

21 - Two cars, passing each other at high speed,are in danger of side swiping because:

A ) Of the increase in air pressure in the space
B ) Of decrease in the velocity of air molecules between them
C ) Of decrease in air pressure in the space between them ✅
D ) Increase in the velocity of air molecules between them

22 - Which of the following is used as a coolant in nuclear reactors?

A ) Heavy water
B ) Cadmium
C ) Liquid sodium ✅
D ) Graphite

23 - Which of the following is good nuclear fuel?

A ) Uranium-238
B ) Neptunium-239
C ) Thorium-236
D ) Plutonium-239 ✅

24 - In an atomic explosion, enormous energy is released which is due to the:

A ) Conversion of neutrons into protons
B ) Conversion of chemical energy into heat energy
C ) Conversion of chemical energy into nuclear energy
D ) Conversion of mass into energy ✅

25 - Optic fibers are mainly used for which of the following?

A ) Communication ✅
B ) Weaving
C ) Musical instruments
D ) Food industry