A smart speaker is connected to the mains electricity supply using a power adapter.
The power input to the smart speaker circuit is 6.0 W6.0\text{ W}6.0 W. The potential difference across this circuit is 15 V15\text{ V}15 V. Calculate the current in the smart speaker circuit.
current=____________________ A \text{current} = \text{\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ A} current=____________________ AThe energy used by the smart speaker each hour is 0.0080 kWh0.0080\text{ kWh}0.0080 kWh. One unit (kWh\text{kWh}kWh) of electrical energy costs 40 cents40\text{ cents}40 cents. Calculate the cost of using the smart speaker for 25 hours25\text{ hours}25 hours.
cost=____________________ cents \text{cost} = \text{\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ cents} cost=____________________ centsThe power adapter contains a transformer. The number of turns NpN_{\text{p}}Np on the primary coil of the transformer is 460046004600. The primary voltage VpV_{\text{p}}Vp supplied to the transformer is 230 V230\text{ V}230 V. The secondary voltage VsV_{\text{s}}Vs of the transformer is 15 V15\text{ V}15 V. Calculate the number of turns NsN_{\text{s}}Ns on the secondary coil of the transformer.
number of turns Ns=____________________ \text{number of turns } N_{\text{s}} = \text{\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_} number of turns Ns=____________________The mains plug for the power adapter includes a fuse that protects the device. Explain how a fuse works.
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.