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Electrical Systems · Part 1 of 4
6 exam-style questions with model answers, plus 8 quick multi-choice questions — every question on this part of the standard, grouped by the 2 pages of notes they come from.
Write a full answer before you reveal the model one. That comparison is where the learning happens.
A cell of emf V has an internal resistance of Ω and supplies a current of A.
Calculate the terminal voltage of the cell.
A cell of emf V and internal resistance Ω is connected to a Ω resistor.
Calculate the current and the terminal voltage. Explain why the terminal voltage is less than the emf.
A car battery has an emf of V and an internal resistance of Ω. The headlights draw A. When the starter motor is engaged it draws an additional A.
Calculate the terminal voltage in each case, and explain fully why the headlights dim when the engine is started. Discuss why a battery in poor condition makes this effect much worse.
At a junction in a circuit, currents of A and A flow in, and two currents flow out. One of the outgoing currents is A.
Calculate the other outgoing current, and state which law you used.
State Kirchhoff's two laws, and explain what conservation principle each one expresses.
A V battery of internal resistance Ω and a V battery of internal resistance Ω are connected in parallel (positive to positive) across a Ω resistor.
Use Kirchhoff's laws to find the current in each branch. Interpret the sign of each result physically, and explain why connecting batteries of different emf in parallel is generally inadvisable.