Connecting ammetersand voltmetersAimTo measure the voltage and current in series and parallel circuitsEquipment• two 2.5 volt globes• six connecting wires (e.g. with alligator clip ends)• 1.5 volt dry cell• ammeter• voltmeterMethodPart A1 Assemble the circuit shown in Figure 7.3.18.2 Record the current and voltage measurements as shown.2 Contrast the brightness of globes in parallel with that of asingle globe.3 Predict the effect of removing a globe when they are:a in seriesb in parallel.4 Predict the circuit in which the cell will go flat most quickly.7.3 PRACTICAL ACTIVITIESA001 2 3 4 50.2 0.4 0.6 0.8 1.0AMPSVVOLTS00 51 1021531.5 V+ –Fig 7.3.18Fig 7.3.171.5 V cell2.5 V globe+ –1.5 V cell + –1.5 V cellconnection post connection post+ –seriesparallel3corkpin strand ofsteel wool234Part B: Series circuits1 Copy each of the circuit diagrams in Figure 7.3.19 into yourworkbook. Use your copy to record all the current and voltagereadings taken at each point as shown.2 Construct the circuit as shown in Figure 7.3.19.3 Use an ammeter to measure the current at each locationindicated by the ammeter symbols in Figure 7.3.19.4 Disconnect the ammeter and then piggyback a voltmeteracross each location indicated by the voltmeter symbols in thesecond diagram in Figure 7.3.19.Note: The red or positive voltmeter terminal connects to the‘side’ of the circuit closest to the positive of the cell or battery.A simple fuseAimTo observe how a fuse worksEquipment• strands of steel wool• cork• two pins• power supply• connecting wires• 2.5 volt globeMethod1 Leaving the power pack turned off, construct the circuit inFigure 7.3.21.2 Gradually increase the power supply voltage from zero,stopping when the fuse melts or the voltage reaches 3 volts,whichever comes first.Questions1 State the voltage at which the fuse melted.2 Explain why a globe was included in the circuit.3 Describe the role of a fuse in a circuit.4 Propose ways in which this fuse could be modified to allowgreater current before melting.Part C: Parallel circuits1 As before, copy the circuit diagrams shown in Figure 7.3.20and use them to record all measurements taken.2 Construct the parallel circuit shown in Figure 7.3.20 andmeasure the current and voltages at the locations shown inthe circuit diagrams.Fig 7.3.20Questions1 Describe the current at various points around the:a series circuitb parallel circuit.2 Describe the voltages around the:a series circuitb parallel circuit.