Distinguish mechanical and electrical energy transfers
Use forces and currents to describe transfers without calling work an energy store.
Mapped to the named 0654 section using teaching from the corresponding single-science course. A 0654-specific review of every Core and Supplement objective is still in progress. Written practice is self-checked; it does not demonstrate supervised laboratory competence or award an official Cambridge grade.
Before you begin
- Distinguish energy stores from pathways.
- Describe a force and the motion it acts through.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which description includes a force acting through movement?
What you will learn
- Recognise transfer by forces as mechanical work.
- Recognise transfer by electric currents as electrical work.
Forces can transfer energy by mechanical work
A force acting through a distance can transfer energy mechanically. A person lifting a load transfers energy that increases the load–Earth gravitational potential store. Friction during sliding can transfer energy from a kinetic store to internal stores of the interacting objects and surroundings. Mechanical work is the transfer, not an eighth store added to the seven-store list.
The direction and movement matter: holding an ideal stationary load does not transfer mechanical energy to that load through displacement, even though a person expends chemical energy internally. Do not identify a force's existence alone with mechanical work done on the selected object. The adjoining Work pathway quantifies aligned force and distance.
A current can transfer energy electrically
A battery can transfer energy electrically through a current to a motor or heater. The battery's chemical store decreases; a motor may increase a load's kinetic or gravitational potential store, while a heater increases internal energy in itself and nearby material. A wire or current is the electrical pathway in this description rather than the final store in the warmed water.
A sequence can contain both transfers: a battery transfers energy electrically to a motor, and the motor transfers energy mechanically to a load. Intermediate components can gain internal energy. Name the pathway at each stage instead of treating 'electrical energy' as a complete account that identifies every source and destination.
Sources for this lesson
Pause and explain
Can the same lift involve electrical and mechanical transfer at different stages?
Worked example
Describe the transfer pathways from a battery through a motor to a lifted load.
Show the worked solution
- The battery supplies energy electrically through a current to the motor.
- The motor transfers energy mechanically to the load through a force acting during motion.
- The load–Earth gravitational potential store increases, with other internal-store gains possible.
Answer Electrical transfer to the motor, then mechanical transfer to the load.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Name pathways from a battery to a motor and from the motor to a moving load.
Give me a hint
Identify the interaction at each stage.
Compare my reasoning
- The current gives an electrical transfer to the motor.
- The pulling force acts through the load's displacement.
- The second stage is mechanical work.
Electrical to motor; mechanical to load.
Look for these in your work
- Name both stages.
- Distinguish pathways from destination stores.
Classify a current heating a wire and friction slowing a sliding block.
Give me a hint
Look for a current in one case and a force through distance in the other.
Compare my reasoning
- The wire receives energy electrically.
- Friction transfers energy mechanically from the block's kinetic store.
- Internal stores increase in the interacting materials and surroundings.
Electrical transfer to the wire; mechanical transfer during sliding friction.
Look for these in your work
- Use the specified interactions.
- Include an internal-store destination.
A student says holding an ideal motionless load necessarily does mechanical work on that load because the support force is large. Explain the limitation.
Give me a hint
Separate displacement of the load from energy use inside the person.
Compare my reasoning
- Mechanical work on the selected load needs relevant displacement.
- The ideal load's displacement is zero.
- The person can still expend chemical energy internally without the proposed mechanical transfer to that stationary load.
No displacement means no mechanical work on this ideal stationary load; internal bodily energy use is a different account.
Look for these in your work
- Identify the selected object.
- Do not equate force magnitude alone with transfer.
Common mistakes
- Work describes a transfer.
- A force without relevant displacement does not establish mechanical work on that object.
- Name both pathways in a motor-driven lift.
What can you explain now?
What pathway transfers energy from a current to a heater?
Compare with the explanation
Electrical work.
The current transfers energy electrically; the heater's internal store can increase.
After trying it yourself, choose your next review. This is your self-assessment.
Your review choice appears on Today. Sign in to sync it across devices.
Make it stick
Explain mechanical and electrical work using a motor lift and distinguish holding a stationary load from lifting it.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.