HKDSE Physics Quick Reference: Electricity at Home Energy Efficiency: Understanding power loss and calculating useful output ( 𝜂 = 𝑃 𝑜 𝑢 𝑡 / 𝑃 𝑖 𝑛 η=P out ​ /P in ​ ). Lighting Devices: Comparing the efficacy and mechanisms of Incandescent Lamps, CFLs, and LEDs. Illuminance: Calculating luminous flux per unit area (lux) and applying the Inverse Square Law. Cooking without Fire: How induction cookers (eddy currents) and microwaves (dielectric heating) work. Air-Conditioning & Heat Pumps: Calculating the Coefficient of Performance (COP) and cooling capacity for DSE Physics. Notes provided by Billy Sir (CUHK Physics Master). Contact for full HKDSE Physics past paper analysis and exam techniques.