Physics · Chapter 8: Circuit rules and V = IR

Year 11 Science · About 18 minutes with activities · Turn your sound on

Chapter 8 · Circuit rules and V = IR

12 ÷ 12 = 1 AI = V ÷ Rₜ

12 ÷ 2.67 = 4.5 Asame as 3 A + 1.5 A

Ammeter: in seriesall the current flows through it

Voltmeter: acrossbefore vs after the bulb

Shared by resistance8 Ω gets twice the voltage of 4 Ω

Extra pathwaymore current, same voltage

Series? Parallel? Both?identify the circuit type first

Parallel part = 2 Ω1/3 + 1/6 = 1/2

Total 4 Ω, I = 3 Aseries: 2 + 2 = 4 Ω; 12 ÷ 4 = 3 A

2 Ω takes 6 V6 V left: 6 ÷ 3 = 2 A, 6 ÷ 6 = 1 A

Series: 3 Vmore current through the bulb

Parallel: 1.5 Vlasts longer

Chapter 8 recap

Series: one pathway. Same current everywhere (Iₜ = I₁ = I₂). Voltages add up, shared in proportion to resistance (Vₜ = V₁ + V₂). Rₜ = R₁ + R₂.
Parallel: currents add up (Iₜ = I₁ + I₂). Every branch has the full voltage (Vₜ = V₁ = V₂). 1/Rₜ = 1/R₁ + 1/R₂, so adding branches lowers Rₜ.
V = IR: identify the circuit type first. Combined circuits: simplify the smaller parts first. Cells in series add voltages; identical cells in parallel last longer.
Next: Chapter 9 · Electrical power and changing circuits

Same battery, same two bulbs. Why does one circuit draw 4.5 times the current?

Chapter 8 · About 18 minutes · sound on

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