Deck 11: Energy, Work, Heat and Power

Question 1

The process by which one form of energy is converted into another form is called

A) torque
B) work
C) heat
D) power

Answer 1

work

Question 2

The process by which energy is transferred from a warmer body to a cooler body is called

A) temperature
B) work
C) heat
D) power

Answer 2

heat

Question 3

The rate at which one form of energy is converted into another form is called

A) velocity
B) work
C) heat
D) power

Answer 3

power

Question 4

The rate at which energy is transferred from a warmer body to a cooler body is called

A) force
B) work
C) heat
D) power

Question 5

The SI unit for energy is the

A) Celsius
B) kelvin
C) joule
D) watt

Question 6

The SI unit for heat transfer is the

A) Celsius
B) kelvin
C) joule
D) watt

Question 7

The SI unit for the rate of heat transfer is the

A) Celsius per second
B) kelvin per second
C) joule per second
D) watt

Question 8

The SI unit for the rate of doing work is the

A) newton metre
B) watt hour
C) joule
D) watt

Question 9

As a customer of your electricity supply company, your energy consumption is measured in

A) kilowatts per hour
B) kilowatt hours
C) megajoules
D) kilowatts

Question 10

How much power is supplied to a 100 W lamp over a period of 3 hours?

A) 33.3 W
B) 100 W
C) 300 W
D) 300 W.h

Question 11

What will happen to the power of a fixed resistance if the applied voltage is doubled?

A) it will reduce by half
B) it will also double
C) it will reduce by one-quarter
D) it will quadruple

Question 12

What will happen to the power of a fixed resistance if the current through it is halved?

A) it will reduce by half
B) it will also double
C) it will reduce by one-quarter
D) it will quadruple

Question 13

If doubling the voltage causes the resulting current to double, what will happens to the power of the circuit?

A) it will reduce by half
B) it will also double
C) it will reduce by one-quarter
D) it will quadruple

Question 14

How much energy is supplied to a 2000-W circuit over a period of 10 min?

A) 1.2 MJ
B) 20 kJ
C) 1.2 W/min
D) 20 kW/s

Question 15

The term 'power loss', when applied to a transmission cable, actually refers to

A) the amount of power lost through heat transfer
B) the rate at which power is lost through heat transfer
C) the amount of energy lost through heat transfer
D) the rate at which energy is lost through heat transfer

Question 16

The 'power rating' of an electric motor refers to its

A) input power
B) output power
C) the difference between its output and input power
D) its energy consumption

Question 17

The 'efficiency' of a motor, or any other electrical machine, is equal to

A) its input power minus its output power
B) its output power minus its input power
C) its input power divided by its output power
D) its output power divided by its input power

Question 18

The 'losses' of a motor, or any other electrical machine, is equal to

A) its input power minus its output power
B) its output power minus its input power
C) its input power divided by its output power
D) its output power divided by its input power

Question 19

What is meant by the term 'windage loss', when applied to a rotating machine?

A) energy-loss in the machine's windings
B) failure to produce torque due to a damaged winding
C) energy-loss overcoming air resistance

Question 20

A higher-wattage lamp has a __________ resistance than a lower-wattage lamp

A) higher
B) lower

Question 21

A 100-W/230-V lamp is connected in series with a 60-W/230-V lamp, across a 230-V supply. Which lamp will be the brightest?

A) 100-W lamp
B) 60-W lamp

Question 22

The sum-total of all the energies associated with the molecules that make up a body is called its

A) heat energy
B) thermal energy
C) internal energy
D) work

Question 23

The difference between the work done on an electric kettle and the heat lost to the surroundings is equal to the

A) increase in temperature of the kettle
B) increase in the power of the kettle
C) increase in the internal energy of the kettle
D) efficiency of the kettle

Question 24

Which has the higher internal energy? A given mass of water at 100 degrees Celsius or the same mass of steam at 100 degrees Celsius?

A) water
B) steam
C) neither -they will both have the same amount of internal energy