Experiment - Energy losses in different wires
In this experiment you will explore how different types of wire affect the flow of electricity through them and practise using an ammeter in a circuit to to measure electric current
To become familiar with the use of an ammeter to measure electric current and to explore how different types of wire affect the flow of electric current through them.
1 x DC variable power supply set at 2V or a 1.5 V dry cell battery
1 x 0-5 A ammeter
1 x 0 to 2 V voltmeter
4 x conducting leads with alligator clips
1 x tapping key switch
At least THREE different wires of the SAME length. e.g. copper, nichrome and constantan. Length about 10 to 20cm.
1 x graphite (carbon) rod (or the lead in a new 3B pencil) . To access the lead in the pencil simply sharpen both ends of the pencil.
The following circuit was set-up with a pair of contacts to attach the wires to be tested.
Note: Care was taken to make sure the leads attached to the ammeter and voltmeter were coming from the correct terminal of the battery to make sure that current flows through the meter in the right direction. Current flowing the wrong way can easily damage ammeters.(Consult your teacher if unsure). The circuit shown if used with a standard laboratory power supply will probably result in a circuit breaker tripping if not used carefully as described below.
The DC power supply was set to the lowest setting (2V) or a 1.5 V battery was used.
A test wire was chosen and attached between the contacts and the length recorded.
The power was then switched ON and OFF quickly, and the reading on the ammeter and voltmeter noted. If the needles DID NOT deflect FULL scale, the power was turned on again and the reading on the ammeter and voltmeter were noted. The circuit was then switched OFF. If the meters are deflected full scale then one way to reduce the deflection is to place a resistor such as a light globe in series in the circuit. Redraw the circuit including a light globe in series and show the revised circuit to your teacher. If your teacher says it is okay, build the new circuit then perform the investigations again. Read the values from the meters and record the results in a table.
The results were recorded in the results Table.
This process was repeated for each of the different test wires.
The results were analysed and a conclusion written.
- Which of the test wires showed the biggest voltage across the wire . The highest voltage reading suggests the most energy difference from one end of the wire to the other. This means a bigger resistance to electricity passing through.
- Which wire was the best conductor?
- Was the # B pencil more resistant to the passage of electricity than the wires?
- The units shown on the ammeter are amperes, but what is the ammeter REALLY recording?
- In this experiment a number of factors were kept constant. These are controlled variables. Identify the controlled variables in this investigation.
- What can you say about the effect of the nature of the material on the conduction of electric current?
- Graphite is pure carbon. A non-metal. What do the results show about the ability of graphite to conduct electricity? How would you rate its resistance compared to metals?