BRAINCAKEGlobal challenges
Revision notes for Global challenges in OCR Combined Science A (J250). Every lesson in BrainCake comes with R.E.C.I.P.E. recall steps, a quick check and spaced reviews.
- Typical speeds in everyday lifeYou should know roughly how fast everyday things move.
- Estimating everyday accelerationsAcceleration is the change in velocity divided by the time taken.
- Converting units and calculating ratesCalculations in physics need SI units: distance in metres (m) and time in seconds (s).
- Measuring human reaction timesYour reaction time is the time between a stimulus, such as seeing something, and your body responding.
- Stopping distances and road safetyWhen a driver sees a hazard, the car does not stop at once.
- Dangers of large decelerationsWhen a vehicle crashes, it decelerates very quickly.
- Energy sources on EarthThe energy we use on Earth comes from a small number of sources.
- Trends in energy resource useThe way we use energy resources has changed a lot over the last 150 years.
- The national grid and voltageThe national grid is the network of power lines (cables hung from pylons or buried underground), transformers and substations that links power…
- Step-up and step-down transformersA transformer changes the potential difference of an alternating current (a.c.) supply.
- Why the national grid is efficientWhen a current passes through a cable it has a heating effect, so some electrical energy is wasted as heat.
- UK mains supplyThe domestic electricity supply in the UK is called the mains.
- Direct and alternating voltageA direct voltage is one where the potential difference keeps the same polarity, so the current is pushed in only one direction around the circuit.
- Live, neutral and earth wiresA three-pin mains plug has three wires.
- Mains safety and the live wireA switch in a mains circuit should always be fitted in the live wire.