Energy Stores and Transfers

Energy is always conserved - it can't be created or destroyed, just moved from one place to another. Think of it like money changing hands rather than appearing from thin air.

You'll encounter four main energy stores: kinetic energy (movement), gravitational potential energy (height), elastic potential energy (stretched springs), and thermal energy (heat). The key equations are straightforward: KE = ½mv², GPE = mgh, and EPE = ½ke².

Power measures how quickly energy transfers $P = E/t$, whilst efficiency tells you how much useful energy you get out compared to what you put in. Most energy eventually becomes thermal energy, which buildings lose through conduction - that's why we need insulation and double glazing.

Quick tip: Energy always flows from hot to cold, never the other way around naturally!

Electrical Circuits

Electrical circuits work because batteries push charged electrons through wires, transferring energy to components like lamps. Think of it like a conveyor belt carrying energy packets around a loop.

Potential difference (voltage) measures how much energy each unit of charge carries, whilst current measures how much charge flows per second. Resistance opposes this flow - it's like friction for electricity.

Ohm's Law $V = IR$ only works for some components. Filament bulbs break this rule because they heat up, making electrons collide more with the wire structure. You can spot this on graphs where the line curves instead of staying straight.

In series circuits, components share the voltage but carry the same current. In parallel circuits, each branch gets the full voltage but current splits between paths.

Particles and Nuclear Physics

Density explains why a cup of iron feels heavier than a cup of cream - iron packs more mass into the same space. You calculate it by measuring mass and volume carefully.

Internal energy is the total kinetic and potential energy of all particles in a substance. When you heat something, you're giving particles more kinetic energy, making them move faster.

Nuclear radiation comes from unstable atomic nuclei trying to become more stable. Alpha particles (helium nuclei) can't penetrate paper, beta particles (fast electrons) can penetrate paper but not aluminium, and gamma rays (high-energy waves) penetrate most materials.

Remember: Always measure background radiation first, then subtract it from your readings to get accurate results.