# Suggested practical

## Investigate the brightness of bulbs in series and parallel

This experiment will investigate how the brightness of bulbs changes depending on whether they are arranged in series or parallel.

### Aim of the experiment

To see how the brightness of bulbs change as they are connected in and , and to measure the across the bulbs and the through the bulbs in series and parallel.

### Method

1. Build a simple series circuit with one bulb and a battery. Add an in the loop and a in parallel with the bulb, as shown in the first diagram.
2. Take notes about the brightness of the bulb, for example whether it is bright or dim. Record the readings from the ammeter in amps (A) and the voltmeter in volts (V).
3. Add another bulb into the loop, as shown in the second diagram. Record the bulb's brightness, current and potential difference.

Repeat this method for each of the following circuits:

Description

Diagram

Circuit 3. Ammeter on each branch, voltmeter across each bulb

Circuit 4. Ammeter on each branch, voltmeter across each bulb

Circuit 5. Ammeter next to each bulb, voltmeter across each bulb

Circuit 6. Ammeter next to each bulb, voltmeter across each bulb

## Results

A suitable results table for each circuit might be:

BulbBrightnessCurrent (A)Potential difference (V)
1
2
3
4

These are example results for Circuit 5 (parallel circuit, two bulbs on one branch, single bulb on the other branch).

BulbBrightnessCurrent (A)Potential difference (V)
1Dim0.403.00
2Dim0.403.00
3Bright as single series bulb0.806.00

### Analysis

• Describe what you notice about the brightness of the bulbs in series and in parallel
• Explain why some bulbs are brighter than others
• Explain what the current and potential difference readings tell you about series and parallel circuits

### Evaluation

When in series, bulbs become dimmer as the potential difference is shared equally across the bulbs. The current reads the same for each component.

In parallel, each branch shows the same potential difference, so the bulbs on one branch will have the same relative brightness. The current for each bulb will add up to the current near the battery.

### Hazards and control measures

HazardConsequenceControl measures
Overheating components - hot bulbBurned fingers, scorched desk Use a heatproof mat. Switch off between readings to ensure components don't get too hot.
Blown bulbShattered glassNever exceed the maximum supply voltage.
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