This question is about electric circuits.
State the name of the instrument used to measure electric current in a circuit.
State the SI unit of electrical resistance.
A student connects a circuit to determine the resistance of a wire. The current in the wire is 0.30 A0.30\text{ A}0.30 A when the potential difference across the wire is 7.5 V7.5\text{ V}7.5 V.
Calculate the resistance of the wire.
The student has several wires of the same material as the one in (b)(i) but with various lengths and thicknesses. She wants to use a wire that has a lower resistance than the wire in (b)(i).
State two ways she can identify a wire with a lower resistance by comparing its length and thickness to the wire in (b)(i).
452 exam-style questions on CIE IGCSE Physics 4.2 Electrical quantities, covering 4.2.1a Positive and negative charge, 4.2.1b Charging by friction and detecting charge, 4.2.1c Electrical conductors and insulators, 4.2.1d Electric fields and electric field patterns, 4.2.2a Electric current, charge and measuring current, 4.2.2b Conduction in metals and the direction of current, 4.2.2c Direct current and alternating current, 4.2.3a Electromotive force, 4.2.3b Potential difference and voltmeters, 4.2.4a Resistance, 4.2.4b Resistance of a metallic wire, 4.2.4c Current–voltage graphs, and 4.2.5 Electrical energy and electrical power. Each one has a worked solution and a mark scheme showing where the marks go.