Circuits from circuit diagrams
Circuit diagrams allow students to make simple records. They also allow teachers to give students summaries of their instructions.
Apparatus and materials
For each student group
Cells, 1.5 V, with holders, 3
Lamps with holders, 3
Leads, 4 mm, 6
Health & Safety and Technical notes
Modern dry cell construction uses a steel can connected to the positive (raised) contact. The negative connection is the centre of the base with an annular ring of insulator between it and the can. Some cell holders have clips which can bridge the insulator causing a 'short circuit'. This discharges the cell rapidly and can make it explode. The risk is reduced by using 'low power', zinc chloride cells not 'high power', alkaline manganese ones.
a Copy the first circuit diagram. Set up the circuit using the equipment provided. Note down what you observe.
b Repeat this procedure for each of the circuits shown.
1 Before this experiment, you may wish to discuss how to draw circuits neatly and what symbols to use. Students need to learn how to draw circuits conventionally using standard symbols and straight lines for the connecting wires. They might also start a glossary of component symbols which will grow as they meet more and more components.
2 For each circuit, a simple note of the brightness of the lamp is all the record that is needed. Recording should not get in the way of early experimenting when familiarity with what the electrical components do is all important. Too many breaks for recording may cause some students to lose the thread of the argument.
3 Students should learn how to construct circuits from circuit diagrams. Too often students copy slavishly from circuit diagrams without beginning to understand what is happening in the circuit. They should be encouraged to discuss the meaning of a circuit diagram. Students should also be encouraged to predict how each circuit will behave, giving a reason, before trying it out.
This experiment was safety-tested in January 2005