Physics 5054 · O Level · Series and parallel circuits
Series and parallel circuits — practice question
A student is comparing the resistances of lamps X and Y.
He assembles the circuit shown in Fig. 2.1.
• He measures the current $I$ in the circuit.
• He measures the potential difference (p.d.) $V$ across lamp X.
• He swaps lamp X for lamp Y and repeats the current and voltage measurements.
• He connects lamp X back into the circuit so that it is in parallel with lamp Y.
• He measures the total current $I$ in the circuit.
• He measures the p.d. $V$ across lamps X and Y in parallel.
The student’s readings are given in Table 2.1.
(a)[2]
Draw the circuit showing lamps X and Y joined in parallel.
(b(i))[1]
Add the column headings to Table 2.1.
(b(ii))[1]
For each lamp arrangement, calculate $R$ with the equation
$R = \frac{V}{I}$.
Put your answers in Table 2.1.
(c)[2]
The student claims that the resistance of lamps X and Y together in parallel is equal to twice the mean resistance of lamp X and lamp Y. This is not correct. Use the data in Table 2.1 to suggest one correct statement about the combined resistance.
Worked solution & mark scheme
This 6-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Lamps X and Y connected in parallel” …