Experiment - Potential difference and energy

Aim

To become aware of the relationship between the supply voltage and the amount of energy that is released from an electric circuit. 
Make a prediction about what you expect to happen as the voltage applied to the device is increased in terms of energy that will be released. Write that prediction down then perform your investigation to test your prediction.

Apparatus (Equipment)

1 x DC variable power supply, with a nominal range from 2 to 12 V. If you don’t have access to a power supply you can substitute with batteries. Just connect the batteries + to – in a line to connect them in series to increase the voltage supplied to the circuit. Each battery will supply 1.5V so two in line will supply 3 V and three 4.5 V and so on. To get to 12 V you will need 8 batteries.

It is probably easier if you connect the batteries to one another with a strip of sticky tape to make sure they maintain contact.

1 x 12V, 21W light globe in a suitable stand

3 x conducting leads with suitable attachments

1 x tapping key switch

Method 

The components were attached in a circuit as shown in the circuit diagram below;

The DC power supply was set to the lowest setting (2 V).
The power was switched ON and careful observations on the appearance of the globe were made.

What do you think will change in the appearance of the globe as the voltage is increased?

Will it be easier and safer to look at light given off or to assess heat given out by the globe?

If you measure light will your measurements be qualitative or quantitative?

The result was recorded in a table. Design your table so it communicates to others your observations in a clear manner. Plan your investigation making a risk assessment before you actually begin.
This was repeated, in turn, for each higher setting on the DC power supply, i.e. 4, 6, 8, 10 and 12 V or 1.5, 3, 4.5, 6, 7.5, 9, 10.5 and 12 V. The results were recorded, analysed and a conclusion written.

This was repeated, in turn, for each higher setting on the DC power supply, i.e. 4, 6, 8, 10 and 12 V or 1.5, 3, 4.5, 6, 7.5, 9, 10.5 and 12 V. The results were recorded, analysed and a conclusion written. The nail and the copper strip were polished with some sandpaper and then inserted into small slits in the surface of the lemon, being sure that they did NOT come into contact (as shown below).

An electrical lead was attached to the nail and another to the copper strip.

The other end of the leads were then touched briefly to a galvanometer and the result observed.

The wires were then reversed on the galvanometer and again touched to the contacts. The result were recorded.

The results were then analysed and a conclusion written.