State, in terms of their structure, why metals are good conductors of electricity.
A cylindrical metal wire W1W_1W1, of length lll and cross-sectional area AAA, has a resistance of 18 Ω18\ \Omega18 Ω. A second cylindrical wire W2W_2W2 having length 2l2l2l and cross-sectional area 3A3A3A, is made from the same metal.
Determine: (i) the resistance of W2W_2W2.
(ii) the effective resistance of W1W_1W1 and W2W_2W2 when connected in parallel.
This parallel pair of wires is connected to a battery made from four identical cells in series, each of electromotive force (e.m.f.) EEE. There is a current in each wire.
(i) State the e.m.f. of the battery in terms of EEE.
(ii) The current in the battery is IBI_{\text{B}}IB, the current in W1W_1W1 is I1I_1I1, and the current in W2W_2W2 is I2I_2I2. Rank these three currents in order from largest to smallest.
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.