Trace energy and explain simple control
Compare energy sources, describe energy conversion and transmission, and model manual, semi-automatic and automatic control.
This lesson is original StudyForA learning support aligned to Cambridge International AS & A Level Design & Technology 9705. It is not Cambridge material or an official mark scheme. Practical activity must follow the learner's centre procedures and trained supervision.
Before you begin
- Read the product brief and identify its intended user and context.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which is a feedback input for an automatic room-temperature control?
What you will learn
- 9705 T11 energy sources
- 9705 T11 energy conversion
- 9705 T11 control systems
Energy moves and changes form
Finite sources include coal, oil and natural gas; renewable examples include water, wind and solar. Compare reliability, availability, environmental effects, cost and the needs of the application rather than labelling one source universally best.
Products can transfer or convert chemical, electrical, thermal, kinetic and potential energy. Mechanisms, machines, engines, turbines and electric motors provide different conversions. Explain the input, conversion, output and losses; efficiency depends on the system boundary and useful output.
Control uses inputs and outputs
A manual system depends on a person to sense and act. A semi-automatic system may control part of a process while a person starts, adjusts or supervises it. An automatic system uses inputs, processing or control, outputs and possibly feedback to respond without continuous human action.
Feedback compares a measured output with a desired condition and allows adjustment. Amplification increases a signal or effect. Identify the sensor or input, control decision, actuator or output and feedback path before evaluating reliability or safety.
Sources for this lesson
Pause and explain
Which principle best supports this lesson: trace energy and explain simple control?
Worked example
A fan turns on when a room exceeds a chosen temperature. Identify its input, output and one possible feedback role.
Show the worked solution
- The temperature sensor measures the room condition as an input.
- The control compares it with the set point.
- The motor and fan provide the output; repeated sensing can update the control decision.
Answer Input: measured temperature. Control: compare with the set point. Output: motor-driven airflow. Feedback occurs when the sensor continues measuring temperature and the control adjusts or switches the fan as the condition changes. A real control also needs safe limits and suitable sensor placement.
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.
A hand-cranked torch lights an LED. Trace the main energy conversions and name one loss.
Give me a hint
Start with the person's chemical energy, then follow movement and electrical output.
Compare my reasoning
- Identify chemical energy in the user's muscles.
- Trace mechanical rotation through the generator to electrical energy.
- Identify light as useful output and one thermal or friction loss.
Chemical energy in the user becomes mechanical rotation, which a generator converts to electrical energy; the LED converts that to light. Some energy is dissipated as heat and friction. The proportions depend on the actual device and cannot be inferred from the diagram alone.
Look for these in your work
- Orders the conversions
- Names useful output
- Identifies a realistic loss
A greenhouse vent opens when temperature rises. Describe the system as input, control, output and feedback.
Give me a hint
Include the measured condition and what the actuator changes.
Compare my reasoning
- Name the temperature as the measured input.
- Explain how a threshold or controller decides whether to act.
- Name the vent movement as output and describe continued measurement.
A temperature sensor provides an input; the controller compares it with a threshold; a motor or mechanism opens the vent. Continued measurement provides feedback so the system can respond as temperature changes. A safe system also needs limits and a manual override where appropriate.
Look for these in your work
- Identifies all system stages
- Describes feedback
- Includes a relevant safety consideration
A remote turbine is proposed for a village workshop. What evidence would help compare it with a grid supply?
Give me a hint
Compare the source and its variability with actual demand, reliability, cost and environmental effects.
Compare my reasoning
- Estimate energy demand over time and required peak power.
- Gather local wind or water resource and maintenance data.
- Compare life-cycle cost, reliability, backup, access and environmental impacts.
Compare measured local resource, demand profile, installation and maintenance costs, reliability, storage or backup requirements and environmental effects. A renewable source is not automatically dependable at every hour, and the grid alternative also needs context-specific evidence.
Look for these in your work
- Uses demand and resource evidence
- Includes reliability and costs
- Compares environmental and access effects
Common mistakes
- Confusing an energy source with an energy form
- Calling a system automatic when a person performs every control action
- Drawing feedback in the wrong direction
What can you explain now?
Which is a feedback input for an automatic room-temperature control?
Compare with the explanation
A sensor measurement of the room temperature
The sensor reports the actual output condition; the set point is the target used for comparison.
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
Draw a simple automatic control loop and label the sensor, decision, output and feedback.
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.