Materials and processing
Materials are what things are made of: wood, metal, plastic, glass, cloth, ceramic. Each has properties, for example strength, weight, how well it takes heat, and whether it rusts. We choose the material whose properties suit the job. Steel is strong, plastic is light, glass takes heat but breaks.
Processing means changing a raw material into a useful shape: cutting, bending, casting (pouring melted metal in a mould), joining by welding or screws, and finishing by painting or polishing.
Good choice also thinks about cost, the environment and whether the part can be recycled.
Energy conversion
Energy cannot be made or destroyed; it only changes form. A machine takes in one form and gives out another. A motor changes electrical energy to motion (kinetic) energy. A fan then moves air.
Not all of it becomes useful. Some becomes heat from friction and from the wires. The share that is useful is the efficiency:
efficiency = useful energy out ÷ energy in × 100 %
A good design saves energy by cutting friction and heat, and by switching off when not needed.
Information management
Many machines decide for themselves. They follow a loop: sensor (reads the world, such as temperature), controller (compares the reading with a rule), and output (a fan, lamp or motor that acts). Information flows like a signal along this loop.
Example rule: if the temperature is 30 °C or more, switch the fan on. Information must be correct, stored safely and kept private if it is personal.
Product maintenance
All parts wear out, so we look after them. Preventive maintenance is done on a schedule before anything fails: cleaning, oiling, tightening. Repair is done after a fault.
A simple loop: inspect → find the fault → repair → record. Records help you see which part fails often. Always switch off and unplug before touching a machine, and wear safety gear.
Try it
Take any small toy or appliance at home (switched off and unplugged). List its materials, the energy it uses, the sensor or switch it has, and one maintenance job. Then change the temperature slider in the 3D and predict when the fan starts before you check.
Key formulas and definitions
- Efficiency = (useful energy out ÷ total energy in) × 100 %
- Wasted energy = energy in − useful energy out
- Information loop: sensor → controller → output
- Maintenance loop: inspect → find fault → repair → record
Worked examples
1. A motor takes in 100 J and gives 70 J of motion. Find the efficiency and the wasted energy.
Efficiency = 70 ÷ 100 × 100 = 70 %. Wasted = 100 − 70 = 30 J, mostly as heat.
2. A fan switches on at 30 °C or more. Is it on at 27 °C? At 33 °C?
At 27 °C it is off, because 27 is below 30. At 33 °C it is on, because 33 is 30 or more.
3. You need a cooking handle that does not get hot and is light. Pick steel, wood or glass.
Wood. It is light and does not pass heat easily. Steel gets hot and glass is heavy and breaks.
Common mistakes
- Saying a machine can have 100 % or more efficiency. Some energy always turns into heat.
- Forgetting units. Energy is in joules (J), temperature in °C.
- Choosing a material only for strength. Weight, cost and heat also matter.
- Fixing a machine that is still plugged in. Always switch off and unplug first.