This will also allow a reading for 100 cm to be taken. Method 1-Place the crocodile clips connecting the wires to the constantan as close together as possible on the constantan. This will effectively give the constantan a length of zero, meaning that any resistance recorded will be that of the connecting wires themselves. This value can be subtracted from each uncorrected reading, giving a corrected reading that only incorporates the reading from the constantan itself. Ensure that one of the crocodile clips is at the very end of the wire, ensuring that only the other will have to be moved, minimising inaccuracy.
2-Place the crocodile clip not at the end ten cm away from the other, record the resistance reading given. Repeat in 10cm increments to 120cm. 3-If time allows, repeat. 4-If repeat readings for the same wire gauge are taken, repeat with a different wire gauge. Main Experiment This experiment will provide a range of data for resistance levels in constantan of different lengths at a range of different voltages. Readings will be taken relative to the voltage, that is the voltmeter will be used as the reference rather than the ammeter.
To ensure a fair test, the same piece of wire will be used for each set of readings, but crocodile clips will be placed on it at the appropriate point o incorporate the correct length into the circuit. Apparatus Voltmeter- The voltmeter will be what the constantan will b e connected to. Rather than having the constantan linked parallel to the meter by connecting wires, it will be placed directly onto the contacts of the meter, still putting it in parallel but ensuring no inaccuracy is built into the results; i. e. the resistance of connecting wires is not incorporated with the resistance of the constantan itself.
Ammeter- Digital meters are always more accurate than analogue ones, therefore it would be preferable to use digital voltmeters and ammeters. However in order to demonstrate a proficiency in using both, I am required to use one of each. I will therefore use a digital ammeter and an analogue voltmeter. Power pack Rheostat (Variable resistor)- this will provide the means by which the potential difference across the wire will be changed. Constantan- Standard Wire Gauge of 26. Lesser than or equal to 120 cm in length, allowing lengths in 10cm increments up to this length. This will also allow a reading for 100 cm to be taken.
Because much more current will be present in the wire than in the preliminary experiment, temperature change in lengths below 50cm may not allow accurate readings to be taken. Therefore only lengths of greater than or equal to 50cm will be used. Method 1-Place the rheostat to its highest value, and ensure that the readings on the ammeter and voltmeter are zero confirming that they are calibrated equally. 2-Place 60 cm constantan under the contacts of the voltmeter, ensuring they are directly linked into the circuit. Lower resistance using the rheostat so that the voltage rises to 1.
Repeat in 1-volt increments up to a value of 6 volts. 3-Take readings for the range of voltages from 1-6 with lengths of constantan going up in 20cm increments to 120cm. 4- If time allows, repeat. 5-If repeat readings for the same wire gauge are taken, repeat with a different wire gauge. Results Preliminary Experiment Multi-meter Test Length in cm Resistance in ohms (Uncorrected) Resistance in ohms (Corrected)Main Experiment Current (Amps).
Resistance (Ohms) Length (cm) Voltage (Volts) Set 1 Set 2 Average Average 6Show preview only The above preview is unformatted text This student written piece of work is one of many that can be found in our GCSE Electricity and Magnetism section.