The voltage measured across the cell is the same for each circuit. Use ideas about energy to explain why this is.

Compare circuit $b$ with circuit $a$. Ahmed measures the voltage across the first lamp in each circuit. He finds that the voltage across the first lamp in circuit $b$ is about half the voltage across the lamp in circuit $a$.
Explain why this is.

We can write the relationship in circuit $a$ and circuit $b$:
Voltage across lamp $1$ in circuit $b$ $<$ the voltage across the lamp in circuit $a$
Which of the following statements is true about the voltage across lamp $1$ in circuit $c$ compared to lamp $1$ in circuit $b$?

Ahmed takes circuit $b$ apart and makes a new circuit $d$. The two lamps are now connected in parallel with each other and the cell.
Draw a diagram of circuit $d$. Label each of the lamps as '$1$' or '$2$'.

Which of these statements shows the correct relationship between the voltage of the cell and the voltages across lamps $1$ and $2$?

Blessy uses circuit to test the relationship between the voltage across the cell and the voltages across each lamp.

Write a method for Blessy's investigation. Assume that Blessy has only one voltmeter.

Blessy extends her investigation to include circuit $b$. She also decides to measure the current in each lamp and the cell. Here is a partly completed table of results.

Which circuit could be used in an investigation to measure both current and voltage?