A student is investigating the potential differences across circuit components.
First, the student connects three lamps, X\text{X}X, Y\text{Y}Y, and Z\text{Z}Z. Lamps X\text{X}X and Y\text{Y}Y are connected in series with each other, and lamp Z\text{Z}Z is connected in parallel with the series combination of X\text{X}X and Y\text{Y}Y.
The student records the total current ItotalI_{\text{total}}Itotal entering the parallel network, the potential difference VXV_{\text{X}}VX across lamp X\text{X}X, and the potential difference VYV_{\text{Y}}VY across lamp Y\text{Y}Y:
Itotal=0.45 A I_{\text{total}} = 0.45\text{ A} Itotal=0.45 A VX=1.2 V V_{\text{X}} = 1.2\text{ V} VX=1.2 V VY=1.5 V V_{\text{Y}} = 1.5\text{ V} VY=1.5 VCalculate the potential difference VseriesV_{\text{series}}Vseries across the series pair of lamps X\text{X}X and Y\text{Y}Y using the equation:
Vseries=VX+VY V_{\text{series}} = V_{\text{X}} + V_{\text{Y}} Vseries=VX+VYCalculate RtotalR_{\text{total}}Rtotal, the combined resistance of the lamps, using the equation:
Rtotal=VseriesItotal R_{\text{total}} = \frac{V_{\text{series}}}{I_{\text{total}}} Rtotal=ItotalVseriesState the unit.
The student rearranges the circuit so that the three lamps are connected in series with each other. They record the potential difference across each lamp in turn:
VX=0.8 V V_{\text{X}} = 0.8\text{ V} VX=0.8 V VY=1.1 V V_{\text{Y}} = 1.1\text{ V} VY=1.1 V VZ=0.9 V V_{\text{Z}} = 0.9\text{ V} VZ=0.9 VCalculate the total potential difference VnewV_{\text{new}}Vnew across the three series lamps using the equation:
Vnew=VX+VY+VZ V_{\text{new}} = V_{\text{X}} + V_{\text{Y}} + V_{\text{Z}} Vnew=VX+VY+VZAnother student suggests that VseriesV_{\text{series}}Vseries should be equal to VnewV_{\text{new}}Vnew. State whether the results support this suggestion and justify your answer by comparing the calculated values.
52 exam-style questions on CIE IGCSE Physics 4.3.2a Series circuits. Each one has a worked solution and a mark scheme showing where the marks go.