This mini-lesson covers Theme B.5 — Current and circuits: current, potential difference and resistance, Ohm's law, electrical power, series and parallel networks, and emf with internal resistance.
Work through each screen, answer the questions as you go (some are reasoning, some are calculations) and collect ⭐ stars. Watch for the HL flag on higher-level extensions. Press Start when you're ready.
Current I is the rate of flow of charge; potential difference V is the energy transferred per coulomb; resistance R opposes the flow.
An ohmic conductor at constant temperature has V ∝ I (a straight line through the origin). A filament lamp is non-ohmic: it gets hotter and its resistance rises, so the graph curves.
Electrical power is the rate of energy transfer. Three equivalent forms (combine with V = IR):
A kettle runs at 230 V drawing 3.0 A.
P = VI = 230 × 3.0 = 690 W
Two arrangements, with opposite rules:
Adding resistors in parallel gives a total resistance smaller than the smallest branch — there are more paths for charge to flow.
Tap an item, then tap the group it belongs to.
A real cell has an internal resistance r, so some energy is lost inside it. Its emf ε is the total energy per coulomb; the terminal pd is what the external circuit gets.
A cell of emf 12 V and internal resistance r = 1.0 Ω drives a 5.0 Ω resistor.
I = ε ÷ (R + r) = 12 ÷ 6.0 = 2.0 A
Terminal pd = IR = 2.0 × 5.0 = 10 V
Tap a statement on the left, then its match on the right.
Basics: I = Δq/Δt; V = IR; ohmic ⇒ constant R
Power: P = VI = I²R = V²/R
Series: same current; resistances add
Parallel: same pd; 1/R = Σ1/Rᵢ; total < smallest
Real cells: ε = I(R + r); terminal pd = ε − Ir
That completes Electric Current & Circuits for IB Diploma Physics HL. Press Finish to see your score.
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Next: test yourself in the Verify stage.