Experiment - Potential difference and current

In this experiment you will examine the effect of increasing the potential difference on the current flowing in a circuit.

Before attempting to do this investigation you should plan your investigation outlining your prediction of how you think changing the voltage applied across the circuit will affect the current flowing in the light globe, an attempt to identify any risks to you or others that could potentially arise during the investigation, a table design for collecting data in an organised way and a graph axes with identified variables to be potted on each axis.



To examine the changes in the current flowing in a circuit as the potential difference (voltage) is increased. 


Apparatus (Equipment)

1 x 12V, 21W light globe and stand

1 x 0 to 5A ammeter

1 x 0 to 12V voltmeter

1 x 2 to 12V variable DC power supply

Suitable conducting leads to connect circuit 


Attach the components together in a circuit as shown in the following diagram.


The Variable power supply was set to the lowest setting - 2 V.

The switch was closed and the readings on the ammeter and voltmeter were recorded. The appearance of the light globe was observed and noted.

This was repeated for each successively higher setting till 12 V was reached.

The results were then analysed, a graph drawn, and then conclusion were noted.



  1. What happened to the reading on the ammeter as the voltage was increased?  What does this mean was happening in the light globe filament?
  2. What did the appearance of the globe indicate about the energy being released by the circuit as the voltage increased?  Are there any other observations that you may have made that support your conclusion? Hint: Consider the temperature of the light globe.
  3. Draw a graph of the independent variable (voltage) versus the dependent variable (current). What does the slope of the line of best fit represent? Hint:  Resistance = volts divided by current.
Electrical cord