Term 1 review: circuits, magnetism, induction and AC

Chapters 1 and 2 give a toolbox, shown in the table. For a circuit, find the equivalent resistance in steps: combine parallel parts, add series parts, find the total current I = VB ÷ (R + r), then go back to the branches. For a two-loop circuit use the Week 3 rules: assume a current in each branch, choose a direction round each loop, count IR as positive when the assumed current agrees with the loop direction, and count an emf as positive when the loop crosses the battery from its negative to its positive pole. A negative answer means that the real current runs opposite to the assumed one. For magnetism, keep μ0 = 1.256 × 10⁻⁶ T·m/A and say which angle you use: θ is the angle that the wire makes with the field in F = BIℓ sin θ, but the angle that the normal to the coil makes with the field in τ = BIAN sin θ. For the meters, the shunt goes in parallel and is tiny, the multiplier goes in series and is large, and an ohmmeter pointer rests at half scale when Rx equals the instrument’s own internal resistance Ri. Always convert units first, write the formula, substitute with units, and check the size of the answer.