State what is meant by the electromotive force (e.m.f.) of an electrical power source.
When connected to a 120 V120\text{ V}120 V supply, a reading lamp has a power rating of 30 W30\text{ W}30 W.
Calculate:
the current in the lamp,
the resistance of the lamp's filament.
An indicator lamp is normally connected to a 6.0 V6.0\text{ V}6.0 V battery and carries a current of 0.25 A0.25\text{ A}0.25 A. The resistance of its filament is 24 Ω24\ \Omega24 Ω.
The reading lamp in (b) and the indicator lamp are connected in series. Students X and Y plan to connect this series combination to a 120 V120\text{ V}120 V supply.
Student X says that the filament of the indicator lamp will melt and the circuit will no longer work. Student Y says that both lamps will light up and stay on.
Show, with a suitable calculation, whether student X or student Y is correct.
136 exam-style questions on CIE IGCSE Physics 4.3 Electric circuits, covering 4.3.1a Circuit diagrams and circuit components, 4.3.2a Series circuits, 4.3.2b Parallel circuits, 4.3.2c Current and potential difference in circuits, 4.3.2d Combined resistance of resistors in parallel, and 4.3.3 Action and use of circuit components. Each one has a worked solution and a mark scheme showing where the marks go.