Components in Series & Parallel Circuits Practice Questions

State the potential difference across the resistor.

potential difference = .............................................................. V

Calculate the resistance of the resistor.

resistance = .............................................................. $\Omega$

Add to Figure 1:

• a voltmeter to measure the potential difference across lamp $L_1$
• a second identical filament lamp, $L_2$, connected in parallel with $L_1$.

The switch is closed. Lamp $L_2$ is then connected in parallel with $L_1$.

What happens to the reading on the ammeter?

Put a cross ( ☒ ) in the box next to your answer.

☐ A the reading falls to zero

☐ B the reading halves

☐ C the reading stays the same

☐ D the reading increases

The filament of lamp $L_2$ then breaks.

State the effect of this on lamp $L_1$.

Explain why the variable resistor is included in the circuit.

The student reverses the connections to the cell so that readings can also be taken for negative values of potential difference.

On the axes below, sketch the graph the student should obtain for the filament lamp.

State the potential difference across the $60\ \Omega$ resistor.

potential difference = .............................................................. V

Calculate the reading on the ammeter.

reading = .............................................................. A

The total resistance of this arrangement is less than the resistance of either resistor on its own.

Explain why.

Describe how the resistance of the thermistor changes as the temperature of the greenhouse increases.

At $10\ ^\circ\mathrm{C}$ the resistance of the thermistor is $4000\ \Omega$.

Calculate the reading on the voltmeter at this temperature.

reading = .............................................................. V

Explain what happens to the reading on the voltmeter as the greenhouse warms up during the day.

Explain what Figure 3 shows about the resistance of the diode.

A filament lamp does not have a constant resistance.

Explain why the resistance of a filament lamp increases as the current in it increases.

A museum model of a Victorian street is to be lit by four identical filament lamps.

• Each lamp is marked $12\ \mathrm{V}$ and has a resistance of $24\ \Omega$ when it is working normally.
• The power supply has a fixed output of $12\ \mathrm{V}$ and can supply a maximum current of $1.5\ \mathrm{A}$.

The designer must decide whether to connect the four lamps in series or in parallel across this supply.

Compare the two arrangements and justify which one the designer should choose.

Your answer should include calculations.