Define energy stores .

Energy stores refer to the different ways in which energy is stored in objects.

True or False? Energy is measured in units of kilograms.

False. Energy is measured in units of joules (J).

Define a system in physics.

A system is an object or group of objects.

True or False? Magnetic and electrostatic are examples of energy stores used in physics.

True. Magnetic and electrostatic are examples of energy stores used in physics. Other examples include kinetic, gravitational potential, elastic, chemical, nuclear, and thermal.

True or False? Objects have energy in their elastic potential store if they are stretched, squashed or bent.

True. Objects have energy in their elastic potential store if they are stretched, squashed or bent.

True or False? All objects have energy in their thermal store, the hotter the object, the less energy it has in this store.

False. All objects have energy in their thermal store, the hotter the object, the more energy it has in this store.

What is the definition of energy transfer pathways ?

Energy transfer pathways are the ways that energy can be transferred from one energy store to another.

True or False? Energy is transferred only through mechanical pathways.

False. Energy can be transferred through various pathways, including mechanical, electrical, heating, and radiation.

Define mechanical working in terms of energy transfer.

Mechanical work is the transfer pathway when a force is exerted over a distance.

True or False? In a falling object, energy is transferred from its kinetic store to its gravitational potential store.

False. In a falling object, energy is transferred from its gravitational potential store to its kinetic store.

State the four energy transfer pathways used in physics.

The four energy transfer pathways used in physics are: mechanical electrical heating radiation

True or False? An example of energy transfer by heating is a hot chocolate warming up cold hands.

True. An example of energy transfer by heating is a hot chocolate warming up cold hands.

Define kinetic energy . (Extended Tier Only)

Kinetic energy is the energy an object possesses due to its motion, determined by its mass and speed.

True or False? Any object in motion has energy in its kinetic energy store. (Extended Tier Only)

True. Any object in motion possesses kinetic energy.

True or False? Kinetic energy is measured in units of joules per second. (Extended Tier Only)

False. Kinetic energy is measured in units of joules (J).

How can kinetic energy be calculated for a given object? (Extended Tier Only)

Kinetic energy can be calculated by multiplying half of the object's mass by the square of its speed.

Define gravitational potential energy . (Extended Tier Only)

Gravitational potential energy is the energy possessed by an object due to its height in a gravitational field.

True or False? Energy is transferred away from an object's gravitational potential store when it is lifted. (Extended Tier Only)

False. Energy is transferred to an object's gravitational potential store when it is lifted.

True or False? Gravitational potential energy is measured in units of newtons per kilogram (N/kg). (Extended Tier Only)

False. Gravitational potential energy is measured in units of joules (J).

True or False? Energy is transferred to an object's gravitational potential store when it falls. (Extended Tier Only)

False. Energy is transferred away from an object's gravitational potential store when it falls.

True or False? The total amount of energy in a closed system can change over time.

False. The total amount of energy in a closed system remains constant; it cannot change over time according to the principle of conservation of energy.

What does an energy flow diagram show?

An energy flow diagram represents energy stores and transfers within a system, showing both the stores and the transfers taking place.

For a system in which energy is conserved, what is an equation relating wasted energy , total energy in and useful energy out ?

The equation representing the conservation of energy is: total energy in = useful energy out + wasted energy

What is a Sankey diagram ? (Extended Tier Only)

Sankey diagrams are graphical representations of energy transfers, characterised by splitting arrows that show the proportions of energy transfers taking place.

What do the different parts of a Sankey diagram represent? (Extended Tier Only)

The left-hand side of a Sankey diagram represents the energy transferred into the system, while the straight arrow pointing to the right represents the useful energy output. The curved arrow represents wasted energy.

True or False? Total energy in a closed system equals useful energy out plus wasted energy. (Extended Tier Only)

True. According to the principle of conservation of energy, the total energy in a closed system is equal to the useful energy out plus the wasted energy.

Define mechanical work done .

Work done is the product of the force applied to an object and the distance over which the force is applied, measured in joules (J) or newton-metres (N m).

True or False? Work is done when a force is applied to an object, regardless of whether the object moves or not.

False. Work is done when a force is applied to an object and results in the object's movement over a distance in the direction of the force.

Define mechanical working energy transfer .

Mechanical working energy transfer is one form of energy transfer when an object moves due to a force acting on it.

Define electrical working energy transfer .

Electrical working energy transfer is one form of energy transfer when a charge moves through a potential difference.

True or False? Work can only be done mechanically.

False. Work can also be done electrically, by heating or by radiation.

True or False? The amount of energy transferred is equal to the work done.

True. The amount of energy transferred (in joules) is equal to the work done (in joules or newton-metres) when any mechanical work is done.

State the conversion between joules and newton metres.

1 joule is equal to 1 newton metre

True or False? Work is done on a ball when it is lifted to a height.

True. Work is done on a ball when it is lifted to a height.

Power is the rate at which energy is transferred or work is done, measured in watts (W).

True or False? Power is the total amount of energy transferred.

False. Power refers to the rate at which energy is transferred or work is done, not the total amount of energy transferred.

True or False? A car has more power if it does the same amount of work in a longer amount of time.

False. A car has more power if it does the same amount of work in a shorter amount of time.

Define the rate of doing work .

The rate of doing work, or power, refers to the amount of work done or energy transferred per unit time. It is measured in watts (W).

True or False? Power and work done are the same quantities.

False. Power is the rate at which energy is transferred or work is done, work done is the total amount of energy transferred.

True or False? Power is often measured in joules (J).

False. Power is typically measured in watts (W), while energy is measured in joules (J).

Efficiency is a measure of the amount of useful power or energy output from a system compared to its total power or energy input. It is often expressed as a percentage.

True or False? Efficiency is a measure of how much useful energy is wasted in an energy transfer.

True. Efficiency measures how much power or energy is transferred usefully, compared to the total power or energy input. Therefore, it is also a measure of how much energy or power is wasted.

True or False? The overall efficiency of a typical coal-fired thermal power station is 30%.

True. The overall efficiency of a typical coal-fired thermal power station is 30%.

True or False? The higher the efficiency of an energy transfer, the more energy is wasted.

False. The higher the efficiency of an energy transfer, the less energy is wasted.

How is efficiency is calculated?

Efficiency is calculated as the ratio of useful power or energy output to total power or energy input, usually expressed as a percentage.

True or False? Efficiency can be given in both ratio and percentage formats. (Extended Tier Only)

True. Efficiency can be expressed as a ratio between 0 and 1, or as a percentage between 0 and 100%.

True or False? Efficiency has units. (Extended Tier Only)

False. Efficiency is a ratio and therefore a dimensionless quantity that does not have any units.

True or False? If an energy transfer is 65% efficient, then 35% of the energy is wasted. (Extended Tier Only)

True. If an energy transfer is 65% efficient, then 35% of the energy is wasted.

IGCSEPhysicsCambridge (CIE)Flashcards1. Motion, Forces & EnergyEnergy, Work & Power

Energy, Work & Power (Cambridge (CIE) IGCSE Physics)

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Cards in this collection (60)

Define energy stores.
Energy stores refer to the different ways in which energy is stored in objects.
True or False?
Energy is measured in units of kilograms.
False.
Energy is measured in units of joules (J).
Define a system in physics.
A system is an object or group of objects.
True or False?
Magnetic and electrostatic are examples of energy stores used in physics.
True.
Magnetic and electrostatic are examples of energy stores used in physics. Other examples include kinetic, gravitational potential, elastic, chemical, nuclear, and thermal.
True or False?
Objects have energy in their elastic potential store if they are stretched, squashed or bent.
True.
Objects have energy in their elastic potential store if they are stretched, squashed or bent.
True or False?
All objects have energy in their thermal store, the hotter the object, the less energy it has in this store.
False.
All objects have energy in their thermal store, the hotter the object, the more energy it has in this store.
What is the definition of energy transfer pathways?
Energy transfer pathways are the ways that energy can be transferred from one energy store to another.
True or False?
Energy is transferred only through mechanical pathways.
False.
Energy can be transferred through various pathways, including mechanical, electrical, heating, and radiation.
Define mechanical working in terms of energy transfer.
Mechanical work is the transfer pathway when a force is exerted over a distance.
True or False?
In a falling object, energy is transferred from its kinetic store to its gravitational potential store.
False.
In a falling object, energy is transferred from its gravitational potential store to its kinetic store.
State the four energy transfer pathways used in physics.
The four energy transfer pathways used in physics are:
- mechanical
- electrical
- heating
- radiation
True or False?
An example of energy transfer by heating is a hot chocolate warming up cold hands.
True.
An example of energy transfer by heating is a hot chocolate warming up cold hands.
Define kinetic energy. (Extended Tier Only)
Kinetic energy is the energy an object possesses due to its motion, determined by its mass and speed.
True or False?
Any object in motion has energy in its kinetic energy store. (Extended Tier Only)
True.
Any object in motion possesses kinetic energy.
What is the equation for calculating kinetic energy? (Extended Tier Only)
The equation for calculating kinetic energy is $E_{k} = \frac{1}{2} m v^{2}$
Where:
- $E_{k}$ = kinetic energy, measured in joules (J)
- $m$ = mass, measured in kilograms (kg)
- $v$ = velocity, measured in metres per second (m/s)
True or False?
Kinetic energy is measured in units of joules per second. (Extended Tier Only)
False.
Kinetic energy is measured in units of joules (J).
What does the term $v$ represent in the kinetic energy equation? (Extended Tier Only)
In the kinetic energy equation, $v$ represents the speed of the object in meters per second (m/s).
Define the term $m$ in the kinetic energy equation. (Extended Tier Only)
In the kinetic energy equation, $m$ represents the mass of the object in kilograms (kg).
How can kinetic energy be calculated for a given object? (Extended Tier Only)
Kinetic energy can be calculated by multiplying half of the object's mass by the square of its speed.
Define gravitational potential energy. (Extended Tier Only)
Gravitational potential energy is the energy possessed by an object due to its height in a gravitational field.
True or False?
Energy is transferred away from an object's gravitational potential store when it is lifted. (Extended Tier Only)
False.
Energy is transferred to an object's gravitational potential store when it is lifted.
What is the equation for calculating gravitational potential energy? (Extended Tier Only)
The equation for calculating gravitational potential energy is $∆ E_{p} = m g ∆ h$
Where:
- $∆ E_{p}$ = change in gravitational potential energy
- $m$ = mass, measured in kilograms (kg)
- $g$ = gravitational field strength, measured in newtons per kilogram (N/kg)
- $∆ h$ = change in height in metres (m)
True or False?
Gravitational potential energy is measured in units of newtons per kilogram (N/kg). (Extended Tier Only)
False.
Gravitational potential energy is measured in units of joules (J).
What does the term $m$ represent in the gravitational potential energy equation? (Extended Tier Only)
In the gravitational potential energy equation, $m$ represents the mass of the object in kilograms (kg).
Define $g$ in terms of the gravitational potential energy equation. (Extended Tier Only)
In the gravitational potential energy equation, $g$ represents the gravitational field strength in newtons per kilogram (N/kg).
True or False?
Energy is transferred to an object's gravitational potential store when it falls. (Extended Tier Only)
False.
Energy is transferred away from an object's gravitational potential store when it falls.
True or False?
The total amount of energy in a closed system can change over time.
False.
The total amount of energy in a closed system remains constant; it cannot change over time according to the principle of conservation of energy.
What does an energy flow diagram show?
An energy flow diagram represents energy stores and transfers within a system, showing both the stores and the transfers taking place.
For a system in which energy is conserved, what is an equation relating wasted energy, total energy in and useful energy out?
The equation representing the conservation of energy is:
total energy in = useful energy out + wasted energy
What is a Sankey diagram? (Extended Tier Only)
Sankey diagrams are graphical representations of energy transfers, characterised by splitting arrows that show the proportions of energy transfers taking place.
What do the different parts of a Sankey diagram represent? (Extended Tier Only)
The left-hand side of a Sankey diagram represents the energy transferred into the system, while the straight arrow pointing to the right represents the useful energy output. The curved arrow represents wasted energy.
State the equation for calculating wasted energy in a Sankey diagram. (Extended Tier Only)
The equation for calculating wasted energy is:
$wasted energy = total energy in - useful energy out$
True or False?
Total energy in a closed system equals useful energy out plus wasted energy. (Extended Tier Only)
True.
According to the principle of conservation of energy, the total energy in a closed system is equal to the useful energy out plus the wasted energy.
Define mechanical work done.
Work done is the product of the force applied to an object and the distance over which the force is applied, measured in joules (J) or newton-metres (N m).
True or False?
Work is done when a force is applied to an object, regardless of whether the object moves or not.
False.
Work is done when a force is applied to an object and results in the object's movement over a distance in the direction of the force.
What is the formula for calculating work done?
The formula for calculating work done is $W = F \times d$
Where:
- $W$ = work done, measured in joules (J) or newton metres (Nm)
- $F$ = force, measured in newtons (N)
- $d$ = distance, measured in metres (m)
Define mechanical working energy transfer.
Mechanical working energy transfer is one form of energy transfer when an object moves due to a force acting on it.
Define electrical working energy transfer.
Electrical working energy transfer is one form of energy transfer when a charge moves through a potential difference.
True or False?
Work can only be done mechanically.
False.
Work can also be done electrically, by heating or by radiation.
True or False?
The amount of energy transferred is equal to the work done.
True.
The amount of energy transferred (in joules) is equal to the work done (in joules or newton-metres) when any mechanical work is done.
State the conversion between joules and newton metres.
1 joule is equal to 1 newton metre
State the relationship between energy transferred and work done.
The relationship between energy transferred and work done is:
$energy transferred (J) = work done (J)$
True or False?
Work is done on a ball when it is lifted to a height.
True.
Work is done on a ball when it is lifted to a height.
Define power.
Power is the rate at which energy is transferred or work is done, measured in watts (W).
True or False?
Power is the total amount of energy transferred.
False.
Power refers to the rate at which energy is transferred or work is done, not the total amount of energy transferred.
True or False?
A car has more power if it does the same amount of work in a longer amount of time.
False.
A car has more power if it does the same amount of work in a shorter amount of time.
What is the formula for calculating power?
The formula for calculating power is:
$P = \frac{W}{t}$ or $P = \frac{Δ E}{t}$
Where:
- $P$ = power, measured in watts (W)
- $W$ = work done, measured in joules (J)
- $Δ E$ = energy transferred, measured in joules (J)
- $t$ = time, measured in seconds (s)
Define the rate of doing work.
The rate of doing work, or power, refers to the amount of work done or energy transferred per unit time. It is measured in watts (W).
True or False?
Power and work done are the same quantities.
False.
Power is the rate at which energy is transferred or work is done, work done is the total amount of energy transferred.
State the equation for calculating energy transferred using power.
The formula for calculating energy transferred using power is:
$∆ E = P \times t$
Where:
- $∆ E$ = $W$ = work done or energy transferred, measured in joules (J)
- $P$ = power, measured in watts (W)
- $t$ = time, measured in seconds (s)
True or False?
Power is often measured in joules (J).
False.
Power is typically measured in watts (W), while energy is measured in joules (J).
Define efficiency.
Efficiency is a measure of the amount of useful power or energy output from a system compared to its total power or energy input. It is often expressed as a percentage.
True or False?
Efficiency is a measure of how much useful energy is wasted in an energy transfer.
True.
Efficiency measures how much power or energy is transferred usefully, compared to the total power or energy input. Therefore, it is also a measure of how much energy or power is wasted.
True or False?
The overall efficiency of a typical coal-fired thermal power station is 30%.
True.
The overall efficiency of a typical coal-fired thermal power station is 30%.
True or False?
The higher the efficiency of an energy transfer, the more energy is wasted.
False.
The higher the efficiency of an energy transfer, the less energy is wasted.
How is efficiency is calculated?
Efficiency is calculated as the ratio of useful power or energy output to total power or energy input, usually expressed as a percentage.
State the equation for calculating efficiency. (Extended Tier Only)
The equation for calculating efficiency is:
$efficiency = \frac{useful power or energy output}{total power or energy input} \times 100 %$
True or False?
Efficiency can be given in both ratio and percentage formats. (Extended Tier Only)
True.
Efficiency can be expressed as a ratio between 0 and 1, or as a percentage between 0 and 100%.
True or False?
Efficiency has units. (Extended Tier Only)
False.
Efficiency is a ratio and therefore a dimensionless quantity that does not have any units.
True or False?
If an energy transfer is 65% efficient, then 35% of the energy is wasted. (Extended Tier Only)
True.
If an energy transfer is 65% efficient, then 35% of the energy is wasted.

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