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Physics · Chapter 9: Electrical power and changing circuits

Year 11 Science · About 17 minutes with activities · Turn your sound on

Chapter 9 · Power and changing circuits
In seriestwo bulbs, one battery
In parallelthe same two bulbs
6 V each · 9 Wthe 12 V is shared
12 V each · 36 Weach gets the full 12 V
At 2 Ω: 2 A, 16 Wbulb: 8 V
At 6 Ω: 1.2 A, 5.76 Wbulb: 4.8 V, dimmer
Bulb brightness lab4 Ω bulbs · 12 V battery

Chapter 9 recap

  • Power is the amount of energy a component transforms per second. P = IV and P = E/t (1 W = 1 J/s). Convert first: m = × 10⁻³, k = × 10³, M = × 10⁶.
  • More power → brighter bulb. When a component heats up, its resistance increases. A higher power device transforms chemical potential energy quicker → shorter battery life.
  • Explaining a change: identify series or parallel → whole circuit (R, V, I) → the component (I, V by V = IR, P by P = IV) → brightness.
  • Next: Chapter 10 · Electric fields and forces

Same bulbs, same battery: why are they brighter in parallel?

Chapter 9 · About 17 minutes · sound on

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