Energy transfers

Learn it by playing

Answer these questions to earn energy, then fish and explore. No account needed.

For teachers: ready-to-use lesson slides, revision notes, diagrams for Energy transfers (KS3 Science, Physics) — use them in your lesson, or run the topic as an interactive class activity your students play as a live game.

Lesson notes

Conservation of Energy

Energy is never **created** or **destroyed**; it is only **transferred** between stores.
The **principle of conservation of energy** states that total energy in a closed system remains constant.
Energy is measured in **Joules (J)**.

Energy Pathways

Energy can be transferred via **four pathways**: mechanically, electrically, by heating, and by radiation.
**Mechanical** transfer: work done by a force moving an object over a distance.
**Electrical** transfer: work done when charges move through a circuit.
**Heating**: energy moves from a hotter object to a cooler object.
**Radiation**: energy transferred by **light**, **sound**, or other electromagnetic waves.

Work Done

**Work done** is another term for energy transferred from one store to another.
Work is done when a **force** causes an object to move.

Energy Stores and Pendulum Example

A pendulum has **gravitational potential energy (GPE)** at its highest point (e.g., 10 J).
As it falls, **mechanical work** transfers GPE to **kinetic energy (KE)**; total energy remains 10 J.
At the lowest point, GPE is minimum and KE is maximum (10 J).
As it rises again, KE transfers back to GPE; at the opposite highest point, GPE = 10 J, KE = 0 J.
Energy is **conserved** throughout the swing.

Efficiency and Wasted Energy

Energy transfers are **not 100% efficient**; some energy is **wasted**.
Wasted energy often ends up in the **thermal energy store** of the surroundings (e.g., air, pendulum).
Air resistance causes the pendulum to eventually stop, transferring KE to thermal energy.

Particle arrangement in solids, liquids, and gases (for context of energy stores).

Slides

Step through every slide for this topic — plus flashcards and revision notes — with a free account.

Practice questions

Free preview — 8 of 40 questions. Sign up to see them all.

1.Which of the following is the principle of conservation of energy?
Easy
- AEnergy can be created but not destroyed.
- BEnergy can be destroyed but not created.
- CEnergy cannot be created or destroyed; it can only be transferred from one store to another.
- DEnergy can be created and destroyed.
2.What is the unit of energy?
Easy
- AWatt (W)
- BJoule (J)
- CNewton (N)
- DPascal (Pa)
3.A pendulum at its maximum height has 10 J of gravitational potential energy. As it swings down, what happens to the total energy of the pendulum?
Medium
- AIt increases to more than 10 J.
- BIt decreases to less than 10 J.
- CIt remains constant at 10 J.
- DIt becomes 0 J at the lowest point.
4.A book on a shelf has 30 J of gravitational potential energy. When it falls to the ground, what is the maximum kinetic energy it can have just before hitting the ground?
Medium
- A0 J
- B15 J
- C30 J
- D60 J
5.In practice, the kinetic energy of a falling object just before it hits the ground is less than the initial gravitational potential energy. Why?
Medium
- ABecause energy is destroyed during the fall.
- BBecause some energy is transferred to the thermal energy store of the surroundings due to air resistance.
- CBecause the object loses mass as it falls.
- DBecause gravitational potential energy cannot be fully converted to kinetic energy.
6.Which of the following is NOT a pathway for energy transfer?
Easy
- AMechanically
- BElectrically
- CChemically
- DBy radiation
7.Energy transferred by light or sound is an example of which pathway?
Easy
- AMechanically
- BElectrically
- CBy heating
- DBy radiation
8.What is meant by 'work done' in physics?
Easy
- AThe total energy stored in an object
- BEnergy transferred from one store to another when a force moves an object
- CThe force applied to an object
- DThe power used by a machine

More questions

9.A bow stores 20 J of elastic potential energy before firing an arrow. After the arrow is fired, what is the total energy in the arrow's kinetic store and the thermal store of the surroundings combined?
Hard
- A0 J
- B10 J
- C20 J
- D40 J
10.Which of the following describes an energy transfer by heating?
Medium
- AA force pushing a box across the floor
- BElectric current flowing through a wire
- CA hot drink cooling down in a room
- DLight from the Sun reaching Earth
11.When a pendulum swings, it eventually stops. Where does the energy go?
Medium
- AIt is destroyed by friction.
- BIt is converted to gravitational potential energy permanently.
- CIt is transferred to the thermal energy store of the surroundings due to air resistance.
- DIt remains in the pendulum as kinetic energy.
12.A battery-powered toy car moves across the floor. Which energy transfer pathway is primarily responsible for the car's movement?
Hard
- AMechanically
- BElectrically
- CBy heating
- DBy radiation
13.A student investigates energy transfers using a toy car on a ramp. The car is released from rest at the top of the ramp and travels down. Which statement correctly describes the energy changes?
Medium
- AGravitational potential energy decreases and kinetic energy decreases.
- BGravitational potential energy decreases and kinetic energy increases.
- CGravitational potential energy increases and kinetic energy decreases.
- DGravitational potential energy increases and kinetic energy increases.
14.A 2 kg mass is lifted vertically through a height of 5 m. The gravitational field strength is 10 N/kg. How much gravitational potential energy is gained by the mass?
Medium
- A10 J
- B20 J
- C50 J
- D100 J
15.A student drops a ball from a height of 2 m. The ball has a mass of 0.5 kg. Ignoring air resistance, what is the kinetic energy of the ball just before it hits the ground? (g = 10 N/kg)
Hard
- A1 J
- B5 J
- C10 J
- D20 J
16.The diagram shows a roller coaster car at the top of a hill. It has 50,000 J of gravitational potential energy. As it descends to the bottom, 10,000 J of energy is transferred to the thermal energy store of the surroundings. What is the kinetic energy of the car at the bottom?
Medium
- A10,000 J
- B40,000 J
- C50,000 J
- D60,000 J
17.Which of the following is an example of energy transfer by radiation?
Easy
- AA kettle boiling water
- BA battery powering a lamp
- CThe Sun warming the Earth
- DA person pushing a trolley
18.A student investigates the efficiency of a motor that lifts a mass. The motor does 200 J of electrical work, but only 150 J of gravitational potential energy is gained by the mass. What is the efficiency of the motor?
Hard
- A25%
- B50%
- C75%
- D100%
19.A pendulum swings from its highest point to its lowest point. At the highest point, the pendulum has 8 J of gravitational potential energy and 0 J of kinetic energy. Ignoring air resistance, what is the total energy of the pendulum at the lowest point?
Medium
- A0 J
- B4 J
- C8 J
- D16 J
20.A student uses a battery-powered fan. Which energy transfer pathway is primarily responsible for the fan blades moving?
Medium
- AHeating
- BRadiation
- CElectrical work
- DMechanical work
21.What is the unit used to measure energy?
Easy
- AWatt (W)
- BJoule (J)
- CNewton (N)
- DVolt (V)
22.A student sets up the circuit shown. The ammeter reads 0.5 A and the bulb is lit. Which energy transfer pathway is taking place in the wires?
Hard
- AMechanical work
- BElectrical work
- CHeating
- DRadiation
23.A ball is thrown upwards. At the highest point of its motion, which energy store is at a maximum?
Easy
- AKinetic energy store
- BGravitational potential energy store
- CElastic potential energy store
- DThermal energy store
24.A student investigates energy transfer by dropping a ball from different heights and measuring the bounce height. The results are shown in the table. Which conclusion is correct?
Hard
- AEnergy is created during the bounce.
- BThe ball loses energy to the surroundings on impact.
- CThe ball gains energy from the ground.
- DThe gravitational potential energy is completely converted to kinetic energy.
25.A student investigates energy transfer using a toy car on a ramp. The car is released from rest at the top of the ramp and travels down. Which statement correctly describes the energy changes?
Medium
- AGravitational potential energy decreases, kinetic energy increases, total energy decreases.
- BGravitational potential energy decreases, kinetic energy increases, total energy remains constant.
- CGravitational potential energy increases, kinetic energy decreases, total energy remains constant.
- DGravitational potential energy decreases, kinetic energy decreases, total energy remains constant.
26.A pendulum swings from its highest point to its lowest point. At the highest point, the pendulum has 8 J of gravitational potential energy and 0 J of kinetic energy. What is the total energy of the pendulum at the lowest point?
Medium
- A0 J
- B4 J
- C8 J
- D16 J
27.The diagram shows a roller coaster car at the top of a hill. It has 50,000 J of gravitational potential energy. As it descends to the bottom, 10,000 J of energy is transferred to the thermal energy store of the surroundings due to friction. What is the kinetic energy of the car at the bottom?
Hard
- A50,000 J
- B40,000 J
- C10,000 J
- D60,000 J
28.A student investigates energy transfer by dropping a ball from different heights and measuring the bounce height. The results are shown in the table. Which conclusion is supported by the data?
Medium
- AThe bounce height is equal to the drop height.
- BThe bounce height increases with drop height but is always less.
- CThe bounce height is independent of drop height.
- DThe bounce height decreases with drop height.
29.In an experiment to measure the efficiency of a motor, a student measures the electrical energy input and the gravitational potential energy gained by a mass. Which additional measurement is needed to calculate efficiency?
Hard
- AThe mass of the motor
- BThe time taken to lift the mass
- CThe height the mass is lifted
- DThe current in the circuit
30.Which of the following correctly states the principle of conservation of energy?
Easy
- AEnergy is never created or destroyed; it is only transferred from one store to another.
- BEnergy can be created but not destroyed.
- CEnergy is always destroyed when work is done.
- DEnergy can be created and destroyed in equal amounts.
31.A bow stores 20 J of elastic potential energy before firing an arrow. After the arrow is fired, the arrow's kinetic energy store is 18 J. What is the most likely reason for the difference?
Medium
- AEnergy is destroyed due to inefficiency.
- B2 J of energy is transferred to the thermal energy store of the surroundings.
- CThe principle of conservation of energy does not apply to bows.
- DThe elastic potential energy store is not fully emptied.
32.What does 'work done' mean in physics?
Easy
- AThe energy transferred from one store to another when a force moves an object
- BThe effort exerted by a person
- CThe power used by a machine
- DThe force applied to an object
33.The diagram shows a roller coaster car at the top of a hill. It has 50,000 J of gravitational potential energy. As it descends to the bottom, 10,000 J of energy is transferred to the thermal energy store of the track and surroundings due to friction. What is the kinetic energy of the car at the bottom?
Medium
- A40,000 J
- B50,000 J
- C10,000 J
- D60,000 J
34.A pendulum swings from its highest point to its lowest point. At the highest point, the pendulum has 8 J of gravitational potential energy and 0 J of kinetic energy. Ignoring air resistance, what is the kinetic energy at the lowest point?
Medium
- A8 J
- B0 J
- C4 J
- D16 J
35.In an experiment to measure the efficiency of a motor, a student measures the electrical energy input and the gravitational potential energy gained by a mass. The student finds that the motor lifts a 2 kg mass through a height of 1.5 m using an electrical energy input of 40 J. The gravitational field strength is 10 N/kg. What is the efficiency of the motor?
Medium
- A75%
- B50%
- C100%
- D25%
36.A student investigates the energy transfers in a bouncing ball. The ball of mass 0.1 kg is dropped from a height of 2.0 m. It rebounds to a height of 1.6 m. The gravitational field strength is 10 N/kg. Calculate the energy lost to the surroundings during the bounce.
Hard
- A0.4 J
- B0.04 J
- C2.0 J
- D0.2 J
37.A student uses a joulemeter to measure the electrical energy supplied to a motor. The motor lifts a 0.5 kg mass through a height of 0.8 m. The joulemeter reads 5 J. The gravitational field strength is 10 N/kg. What is the efficiency of the motor?
Medium
- A80%
- B20%
- C100%
- D50%
38.A student sets up a simple pendulum. The bob has mass 0.2 kg. The student pulls the bob sideways so that it is 0.1 m higher than its lowest point, then releases it. The gravitational field strength is 10 N/kg. Ignoring air resistance, what is the maximum speed of the bob during its swing?
Hard
- A1.4 m/s
- B2.0 m/s
- C0.7 m/s
- D1.0 m/s
39.Which of the following is the correct unit for energy?
Easy
- AJoule (J)
- BWatt (W)
- CNewton (N)
- DAmpere (A)
40.In an experiment to investigate energy transfer by heating, a student places a metal block on a tripod and heats it with a Bunsen burner. The student measures the temperature rise of the block using a thermometer. Which of the following would improve the accuracy of the experiment?
Medium
- AUsing an insulating mat under the block
- BUsing a larger Bunsen burner flame
- CStirring the block while heating
- DUsing a glass block instead of a metal block

Revision notes

## Energy Transfers - **Conservation of Energy**: Energy is never created or destroyed; it is only transferred from one energy store to another. - **Unit of Energy**: Joule (J). - **Four Pathways for Energy Transfer**: 1. **Mechanically**: Work done when a force is applied over a distance. 2. **Electrically**: Work done when charges move through a circuit. 3. **By heating**: Transfer from a hotter object to a cooler object. 4. **By radiation**: Energy transferred by light, other electromagnetic waves, or sound. - **Work done** is another way of saying energy transferred from one store to another. - **Example: Pendulum** - At maximum height: GPE = 10 J, KE = 0 J. - At lowest point: GPE = 0 J, KE = 10 J (if no energy losses). - Total energy remains constant (conservation). - Eventually stops due to air resistance; energy is 'wasted' by raising the thermal energy store of surroundings. - **Efficiency**: Energy transfers are not 100% efficient; some energy is transferred to less useful stores (e.g., thermal energy of surroundings).

Conservation of energy: Energy is never created or destroyed; it is only transferred from one energy store to another.
Joule (J): The unit of energy.
Mechanical work: Work done on an object when a force is applied over a distance.
Electrical work: Work done when charges move through a circuit.
Heating: Transfer of energy from a hotter object to a cooler object.
Radiation: Transfer of energy by light, other electromagnetic waves, or sound.
Work done: Another way of saying energy transferred from one store to another.
Gravitational potential energy (GPE): Energy stored due to an object's height above the ground.
Kinetic energy (KE): Energy stored due to an object's motion.
Elastic potential energy (EPE): Energy stored in a stretched or compressed elastic object.

Flashcards

State the principle of conservation of energy.

Energy is never created or destroyed; it is only transferred from one energy store to another.

What is the unit of energy?

The unit of energy is the Joule (J).

What are the four pathways for energy transfer?

Mechanically, electrically, by heating, and by radiation.

What is mechanical work?

Mechanical work is done on an object when a force is applied over a distance.

What is electrical work?

Electrical work is done when charges move through a circuit.

What is energy transfer by heating?

The transfer of energy from a hotter object to a cooler object.

What is energy transfer by radiation?

Energy transferred by light (or any electromagnetic wave) and sound.

What does 'work done' mean?

Work done is another way of saying energy transferred from one store to another.

A pendulum at maximum height has 10 J of GPE. As it falls, what happens to its GPE and KE?

Its GPE store empties and its kinetic energy (KE) store fills to 10 J.

When a pendulum swings from the bottom to the maximum height, what energy transfer occurs?

Its KE store empties and its GPE store fills back to the original amount.

Why does a pendulum eventually come to a stop?

Due to air resistance; energy is wasted by raising the thermal energy store of the surroundings.

Are energy transfers usually 100% efficient?

No, generally energy transfers are not 100% efficient; some energy is wasted.

A book on a shelf has 30 J of GPE. It falls. How much KE does it have just before hitting the ground (ignoring air resistance)?

30 J, because GPE is converted to KE and total energy is conserved.

In practice, why would the KE of a falling book be less than the initial GPE?

Because some energy is transferred to the thermal energy store of the surroundings due to air resistance.

What is gravitational potential energy (GPE)?

Energy stored by an object due to its position in a gravitational field, e.g., height above ground.

What is kinetic energy (KE)?

Energy stored by an object due to its motion.

What is elastic potential energy (EPE)?

Energy stored in a stretched or compressed elastic object, such as a bow or spring.

In a pendulum, at the highest point, what is the KE?

Zero, because the pendulum is stationary at the highest point.

In a pendulum, at the lowest point, what is the GPE?

Zero (if we take the lowest point as reference), because height is minimum.

What happens to the total energy of a pendulum as it swings?

The total energy remains constant (conserved), but it is transferred between GPE and KE.

Name one way energy is 'wasted' in a pendulum.

Energy is transferred to the thermal energy store of the pendulum and nearby air due to air resistance.

What is the energy transfer pathway when a force moves an object?

Mechanically (mechanical work).

What is the energy transfer pathway when a current flows?

Electrically (electrical work).

What is the energy transfer pathway when a hot object warms a cold one?

By heating.

What is the energy transfer pathway when light travels from the Sun to Earth?

By radiation.

Unlock all 40 questions, flashcards & more

Create a free account to see every question, the slides, flashcards and revision notes for this topic.

Past papers

Past-paper practice for this topic is coming soon.

Coming soon