Define electric current and potential difference, and give their SI units. How are an ammeter and a voltmeter connected in a circuit?

1. 1 · Define current. Electric current is the rate of flow of charge, I = Q/t. SI unit: ampere (1 A = 1 C/s).
2. 2 · Define potential difference. The work done to move a unit charge between two points, V = W/Q. SI unit: volt (1 V = 1 J/C).
3. 3 · Draw the circuit. [Circuit: cell, closed plug key, bulb and ammeter in series; voltmeter across the bulb; + and − marked on both meters]
4. 4 · State the connections. Ammeter in series, so all the current passes through it. Voltmeter in parallel, across the two points.
5. 5 · Real life. A charger label such as 5 V, 2 A gives both quantities.
6. 6 · Close in one line. Current is the flow of charge; potential difference is the push that causes it.

Scoring tip: Write each formula with its unit, for example I = Q/t, unit ampere. Mark + and − on the meters in your diagram.