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WAEC questions for "Physics :: Energy"
Q1

A body of volume 0.046m3 is immersed in liquid of density 980 km-3 with ¾ of its volume submerged . Calculate the upthrust on the body . [ g = 10 ms -2 ]

A

11.27N

B

33.81 N

C

112.70 N

D

338 .10N

E

Answer: C

Energy
Q2

Electrical energy is measured in 

A

ampere

B

coulomb

C

Kilowatt-hour

D

Kilowatt

E

Answer: C

Energy
Q3

A stone of mass 0.50kg is dropped from a height of 12 m . Calculate its maximum kinetic energy. [ g= 10ms-2 ]

A

3.0J

B

6.0J

C

30.0J

D

60.0J

E

Answer: D

Energy
Q4

A machine of efficiency 80% is used to lift a box. If the effort applied by the machine is twice the weight of the box, calculate the velocity ratio of the ratio of the machine. 

A

0.50

B

0.63

C

0.80

D

1.60

E

Answer: B

Energy
Q5

A faulty thermometer registers 102.5oC at 100oC. If the thermometer has no zero error, what will it register at 55oC?

A

54.6oC

B

55.0oC

C

56.0oC

D

56.4oC

E

Answer: D

Energy
Q6

As a bicycle tyre was being pumped up, it was noticed that contrary to Boyle's law the volume increased as the pressure increased. The best explanation of this is that Boyle's law is only true for 

A

ideal gases

B

a fixed mass of gas

C

a mixture of gases

D

a gas at variable temperature

E

Answer: B

Energy
Q7

It takes 4 minutes to boil a quantity of water using an electrical heating coil. How long will it take to boil the same quality of water using the same heating coil if the current is doubled? [ Neglect any external heat losses] 

A

8 minutes 

B

4 minutes 

C

2 minutes 

D

1 minutes

E

Answer: C

Energy
Q8

When table salt is added to ice, the melting point of the ice 

A

is raised

B

is lowered

C

remains unchanged 

D

is first raised, then lowered

E

Answer: B

Energy
Q9

Which of the following factors affect the rate of evaporation of a liquid? 

I. Exposed surface area

II. Temperature of the surroundings

III. Thermal capacity of the liquid

IV. Relative humility of the surroundings

 

A

II and III only 

 

B

II, III and IV only

C

I , III and IV only

D

I, II and IV only

E

Answer: D

Energy
Q10

Which of the following instruments is used to measure relative humidity?

A

Hydrometer

B

Barometer

C

Hypsometer

D

Hygrometer

E

Answer: D

Energy
Q11

A rectangular block of dimensions 2.0mx1.0mx0.5m weighs 200 N. Calculate the maximum pressure exerted by the block on a horizontal floor 

A

100Nm-2

B

200Nm-2

C

300Nm-2

D

400Nm-2

E

Answer: D

Energy
Q12

Which of the following devices converts heat energy to electrical energy?

A

Transformer

B

Dynamo

C

Thermocouple

D

Thermostat

E

Answer: C

Energy
Q13

An object  of mass 0.25 kg moves at a height h above the ground with a speed  of 4ms-1 . If its electrical energy at height is J, determine the value of h. [ g= 10ms-1]

A

0.8m

B

4.0m

C

4.8m

D

5.6m

E

Answer: B

Energy
Q14

which of the following equations for the efficiency of a machine is correct?

A

Efficiency = Velocity Ratio                 

                        Mechanical Advantage          x 100%

B

Efficiency = Input        

                      Output            X 100%

C

Efficiency  =  Load distance 

                             Effort distance            X        100%

D

Efficiency =  Mechanical  Advantage 

                            Velocity Ratio                                             X    100%

E

Answer: D

Energy
Q15

The design of the thermostat of an electric iron is based on the 

A

emission of electrons from metals when heated 

B

increase in size of metals when heated  

C

increase in the  density of metals when heated 

D

change in the mass of metals when heated 

E

Answer: B

Energy
Q16

A metal rod of length 50cm is heated from 40oC to  80oC. if the linear expansivity  of the material is α 

A

20α 

B

200α 

C

2000α 

D

20000α 

E

Answer: C

Energy
Q17

The cubic expansivity of a certain gas at constant pressure is 1/273 K-1. If a given mass of the gas is held at constant pressure and its volume of the gas at 273oc.

A

273 m3

B

546m3

C

819m3

D

092m3

E

Answer: B

Energy
Q18

Water of mass 1.5 kg ids heated from 30oC to 80oC using an electric kettle which is rated 5A, 239V. Calculate the time taken to reach the final temperature.

[Specific heat capacity of water = 4200 Jkg-1 K -1

A

4.57 minutes 

B

5.02 minutes

C

7.30 minutes 

D

10.04 minutes

E

Answer: A

Energy
Q19

The working principle of a pressure cooker is based on on the 

A

increase in the volume steam inside it

B

complete trapping of heat inside it

C

increase in the pressure of pot

D

decrease in the pressure of pot

E

Answer: B

Energy
Q20

It takes a shorter time for a liquid to boil at the top of a mountain than at the base because at the top, the

A

temperature is higher

B

pressure is lower

C

humidity is higher

D

temperature is constant

E

Answer: B

Energy
Q21

Mechanical energy can be either 

A

Kinetic or electric 

B

chemical or potential 

C

potential or kinetic 

D

electric or heat

E

Answer: C

Energy
Q22

The ice and stream points on a mercury-in-glass thermometer are 10cm and 30cm respectively. Calculate the temperature in degree celcius, when the mercury meniscus is at the 14 cm mark

A

20oC

B

30oC

C

34oC

D

70oC

E

Answer: A

Energy
Q23

Which of the following surfaces will radiates heat energy best? 

A

Red surface

B

White surface

C

Black surface 

D

Yellow surface

E

Answer: B

Energy
Q24

Which of the following statements distinguishes thermal conduction from convection?

I. Conduction requires a material medium while convection does not 

 

A

I and II only 

B

II and III only 

C

I and III only

D

I , II and III

E

Answer: B

Energy
Q25

A cube made of a metal of linear expansivty α is heated through a temperature θ. If the initial volume of the cube is Vo, the correct expression for the increase in volume of the cube is 

A

1/3 α Voθ

B

1/2 α Voθ

C

2 α Voθ

D

3 α Voθ

E

Answer: D

Energy
Q26

A relative density bottle of volume 50cm3 is completely filled with a liquid at 30oC. It s then heated to 80oC such that 0.75cm3 of the liquid is expelled. Calculate the apparent cubic expansivity of the liquid .

A

0.00030K-1

B

0.00032K-1

C

0.01970 K-1

D

0.02030 K-1

E

Answer: A

Energy
Q27

A body of mass 200g and specific heat capacity  0.4 Jg-1K-1 cools from 37oC to 31oC. Calculate the quantity of heat released by the body 

A

4800 J

B

1200 J

C

480 J

D

202 J

E

Answer: C

Energy
Q28

According to the kinetic theory of gases, which of the following properties of a gas an be affected by the collision of the gas molecules with the walls of its container ? 

A

Temperature

B

Energy

C

Viscosity

D

Pressure

E

Answer: A

Energy
Q29

The pressure of a fixed mass of a idea gas at 27oC is 3 Pa. The gas is heated at a constant volume until its pressure is 5 Pa . Determine the new temperature of the gas

A

100oC

B

227oC

C

273oC

D

500oC

E

Answer: C

Energy
Q30

Which of the following sources of energy is renewable?

A

Petroleum

B

Charcoal

C

Hydro

D

Nuclear

E

Answer: C

Energy
Q31

Which of the following statements about the mouth piece of a telephone is correct? It converts sound energy into

A

acoustic energy

B

mechanical energy

C

electrical energy

D

heat energy

E

Answer: C

Energy
Q32

The potential energy string of force constant k which has been extended by x meters is expressed as

A

1/2 Kx2

B

Kx2

C

1/2 Kx

D

Kx

E

Answer: A

Energy
Q33

The engine of train produces a force of 3000N when moving at 30 ms-1. Calculate the power of the engine.

A

1.00 x 102W

B

3.00 X 104 W

C

9.00 X 104 W

D

3.00 x 105 W

E

Answer: C

Energy
Q34

A block and tackle system has six pulleys. A force of 50 N applied to it lifts a load of weight W. If the efficiency of the system is 40%, calculate W

A

300N

B

200N

C

140N

D

120N

E

Answer: D

Energy
Q35

The sagging of overhead electrical cables is the consequence of

A

linear expansivity

B

superficial expansivity

C

cubic expansivity

D

conductivity

E

Answer: A

Energy
Q36

The sliver surface in vacuum flask reduces heat loss due to

A

conduction

B

convection

C

radiation

D

evaporation

E

Answer: C

Energy
Q37

How long will it take gto heat 3kg of water from 28oC to 88oC in an electric kettle taking 6A from a 220V supply? [ specific heat capacity of water = 4180 J kg-1K-1 ]

A

120s

B

570s

C

600s

D

836 s

E

Answer: B

Energy
Q38

The amount of energy required to change a kilogram of ice block into water without a change in temperature is

A

heat capacity of ice

B

specific heat capacity

C

specific latent heat of vapourization of ice

D

specific latent heat of fussion of ice

E

Answer: D

Energy
Q39

A quantity of stream at 100oC condenses to water at the same temperature by releasing 6.9X104J of energy. Calculate the mass of the condensed steam. [specific latent heat of vapourisation of water = 2.3 x 106 J kg-1]

A

3.0 X 10-1 kg

B

3.0 X 10-2kg

C

3.0 X 10-3 kg

D

3.0 X 10-4 kg

E

Answer: B

Energy
Q40

The temperature of liquid fall after some of it has evaporated because

A

the liquid left is smaller in volume and the breeze easily cools it

B

the more energenic molecules have escaped into the atmosphere

C

the liquid left has less latent heat

D

after evaporation impurities are left   behind

E

Answer: B

Energy
Q41

Which of the following simple machines is a second class level?

A

Wheel barrow

B

Crowbar

C

Claw hammer

D

Seesaw

E

Answer: A

Energy
Q42

Which of the following quantities has the same unit as energy?

A

Power

B

Work

C

Force

D

Momentum

E

Answer: B

Energy
Q43

Which of the following sources of energy is renewable?

A

Sun

B

Petroleum

C

Coal

D

Uranium

E

Answer: B

Energy
Q44

The lower and upper fixed points of a thermometer are 30mm and 180mm respectively. Calculate the temperaturte in degrees celsius when the thermometer reads 45mm.

A

10.0o C

B

15.0o C

C

20.0o C

D

30.0o C

E

Answer: A

Energy
Q45

A body of mass m has a specific heat capacity s and a heat capacity c. If the temperature of the body changes by θo C, which of the following equations is correct? 

A

ms0 = mc-1

B

ms=C

C

ms = sθ

 

D

ms = cθ

E

Answer: B

Energy
Q46

An immersion heater rated 400W, 220V is used to heat a liquid of mass 0.5kg . If the temperature of the liquid increases uniformly at the rate of 2.50C per second, calculate the specific heat capacity of the liquid. [Assume no heat is lost ]

A

1100Jkg-1 K-1

B

320Jkg-1 K-1

C

200Jkg-1 K-1

D

176Jkg-1 K-1

E

Answer: B

Energy
Q47

Water falls through a height of 50cm. Determine the temperature rise of water at the bottom of the fall. [Neglect energy losses. Specific heat capacity of water = 4200Jkg-1 K-1,  g= 10ms-2 ]

A

0.119oC

B

0.840oC

C

1.190oC

D

8.400oC

E

Answer: A

Energy
Q48

The energy required to change a solid to liquid at constant temperature is called

A

thermal capacity

B

specific heat capacity

C

latent heat of fussion

D

latent heat of vapourisation

E

Answer: D

Energy
Q49

Which of the following statements about boiling and evaporation at atmosphere pressure is correct?

A

Evaporation and boiling of water take place at 100oC

B

Evaporation of water takes place at a temperature greater than 100oC, while boiling of water takes place at 100oC

C

Evaporation of water takes place at 100oC wehile boiling of water takes place at a higher temperature

D

Boiling takes place at 100oC while evaporation may take place at temperatures lower than  100oC

E

Answer: D

Energy
Q50

Which of the following statements is correct?

A

the density of a liquid decreases when it expands

B

the densities of liquid increase when the liquid are heated

C

the real expansivity of a liquid is less its apparent expansivity

D

a liquid changes to solid when heated to a sufficiency high temperature

E

Answer: A

Energy
Q51

The pressure exerted by a given mass of gas in a container

A

decreases if the container is heated

B

increases if the molecules of the gas move faster.

C

increases if the volume of the container is doubled

D

decreases as the kinetic energy of the gas molecules increases

E

Answer: B

Energy
Q52

A driver is 5.2m below the surface of water of density 1000kgm-3 . If the atmospheric pressure is 1.02 x 105 Pa, calculate the pressure on the driver . [ g= 10 mS-2 ]

A

6.20 x 104 Pa

B

1.02 x 105 Pa

C

1.54 x 105 Pa

D

5.20 x 105 Pa

E

Answer: C

Energy
Q53

Calculate the change in volume when 90 g of ice is completely melted.

[ density of water = 1 g cm3, density of ice=0.9 g cm3]

A

0.00m3

B

9.00m3

C

10.00m3

D

90.00m3

E

Answer: C

Energy
Q54

A machine of velocity ratio 5 is used in lifting a load with an effort of 500N. If the machine is 80% efficient, determine the magnitude of the load.

A

2500N

B

2000N

C

900N

D

625N

E

Answer: B

Energy
Q55

When compared with water, mercury is preferred as a thermometric liquid because it

A

has higher density

B

has a lower specific heat capacity

C

exhibits anomalous thermal expansion

D

contains molecules which have very strong adhesive forces

E

Answer: B

Energy
Q56

Which of the following values on the absolute scale of temperature is the ice point?

A

0K

B

32K

C

100K

D

273K

E

Answer: D

Energy
Q57

On a cold day, a concrete floor feels colder to the bare foot than a mat on the same floor because the

A

mat is a better conductor of heat than the foot

B

mat loses heat to the bare foot at a faster rate

C

mat is a better conductor of heat than the floor

D

concreate floor is a better conductor of heat than the mat

E

Answer: D

Energy
Q58

When a metal ball is heated through 30oC, its volume becomes 1.00180ms-3 . If the linear expansivity of the material of the ball is 2.0 x 10-5 K-1 , calculate its original volume.

A

1.0000cm3

B

1.0020cm3

C

1.0036cm3

D

1.0180m3

E

Answer: A

Energy
Q59

A faulty barometer reads 72.6cm Hg when the atmospheric pressure is 75.0 cmHg. Calculate the atmospheric pressure when this barometer reads 72.0 cm Hg.

A

79.4cm Hg

B

74.4cm Hg

C

74.2cm Hg

D

69.4cm Hg

E

Answer: B

Energy
Q60

On the basis of the kinetic theory, an increase in the temperature of a fixed volume of an ideal gas causes 

A

an increase in the number of the gas molecules

B

a decrease in the density of the gas

C

an increase in the average speed of the gas molecules

D

a decrease in the pressure exerted by the gas

E

Answer: C

Energy