大象传媒

Investigating bulb brightness experiment

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 or .

Aim of the experiment

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

Method

Circuit containg a cell, ammeter and a lamp with a voltmeter in parallel.
This is a circuit showing two bulbs connected to a voltmeter each. There is one ammeter and one cell on the top row.
  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 brightness, current and potential difference for each bulb.
  4. Repeat this method for each of the following circuits:

Description

Diagram

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

A circuit with two lamps in parallel to each other and both connected to a voltmeter each. There is an ammeter on both of the lamp鈥檚 rows.

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

A circuit with three lamps on three rows which are each connected to a voltmeter. There are three ammeters also on each row.

Circuit 5: Ammeter on each branch, voltmeter across each bulb

A circuit with three lamps and three voltmeters connected to the lamps, and two ammeters at the end of both rows.

Circuit 6: Ammeter on each branch, voltmeter across each bulb

A circuit with four lamps, four voltmeters, and two ammeters all in parallel across two rows.

Results

A suitable results table for each circuit might be:

BulbBrightnessCurrent (A)Potential difference (V)
1.........
2.........
3.........
4.........
Bulb1
Brightness...
Current (A)...
Potential difference (V)...
Bulb2
Brightness...
Current (A)...
Potential difference (V)...
Bulb3
Brightness...
Current (A)...
Potential difference (V)...
Bulb4
Brightness...
Current (A)...
Potential difference (V)...

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
Bulb1
BrightnessDim
Current (A)0.40
Potential difference (V)3.00
Bulb2
BrightnessDim
Current (A)0.40
Potential difference (V)3.00
Bulb3
BrightnessBright as single series bulb
Current (A)0.80
Potential difference (V)6.00

Analysis

  1. describe what you notice about the brightness of the bulbs in series and in parallel
  2. explain why some bulbs are brighter than others
  3. 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 or scorched deskUse a heatproof mat and switch off between readings to ensure components don't get too hot
Blown bulbShattered glassNever exceed the maximum supply voltage
HazardOverheating components - hot bulb
ConsequenceBurned fingers or scorched desk
Control measuresUse a heatproof mat and switch off between readings to ensure components don't get too hot
HazardBlown bulb
ConsequenceShattered glass
Control measuresNever exceed the maximum supply voltage