• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Resistance of Wire Investigation

Extracts from this document...


Alexander Kilpatrick       GCSE Coursework - Plan                Page                               01/05/2007

Resistance of Wire Investigation



How the resistance of wire varies with its length.


I hypothesise that increasing the length of wire in a circuit will increase the resistance in a circuit.

Resistance involves collisions of the current-carrying charged particles with fixed particles that make up the structure of the conductors or wires.

Therefore I predict that increasing the length of wire will increase the number of times electrons collide inside the wire.

The resistance (R) of an object is measured in Ohms (Ω) and is determined by a property of the substance of which it is composed, known as the resistivity (image01.png), and by the length (l) and cross-sectional area (A) of the object, and by the temperature. At a given temperature, the resistance is proportional to the object's resistivity and length, and inversely proportional to its cross-sectional area.

This formula is:  

                        R =image01.pngl/A

It is easy to understand how the dimensions of a material affect resistance, in equation form: the longer the wire, the greater the resistance to the flow of charge.

...read more.


A) for the constantan wire is (π x 0.0002252) = 1.590431281 x 10-7 m2.The values for l are the independent variables for this experiment and can be substituted easily as we progress.

I will predict some of the resistance (R) values for the forthcoming experiment using the formula R =image01.pngl/A . These predictions will be useful for testing the reliability of the results I obtain in the experiments.

Length of wire (l) - m

Resistivity of Constantan

 (image01.png) -  Ωm at 20oC.

Area of cross-section (A) – m2

image01.pngl/A = Resistance

 (R) - Ω


4.9 x 10-7

1.590431281 x 10-7



4.9 x 10-7

1.590431281 x 10-7



4.9 x 10-7

1.590431281 x 10-7



4.9 x 10-7

1.590431281 x 10-7



4.9 x 10-7

1.590431281 x 10-7


To clarify the reliability of my experiment I will draw a graph to illustrate the resistivity of constantan. The graph will have the Restance results (R) on the y-axis, and the length divided by the cross-sectional area (l/A) on the x-axis.

...read more.


controlled variableCross-section of constantan wire. As demonstrated in the formula R =image01.pngl/A, the cross-section of the wire has a direct effect on the resistance and therefore the current and voltage. Consequently we will keep this constant as a controlled variableTemperature. This will also be kept constant at room temperature, so is a controlled variableLength of constantan wire. This is what I am changing as my independent variable

Preliminary Experiment

To ensure this experiment will work, the method is suitable and the range of readings is appropriate, I will conduct a preliminary experiment.


Length of Wire (m)

Voltage (V)

Current (A)

Resistance (Ω)



Off scale






From the preliminary experiment I noticed that the ammeter used had too small a limit (0-2 Amps) and hence the current result for 1m of wire was off the ammeter’s scale.

Therefore I will adapt my method to having an appropriate ammeter for coping with larger amounts of current, i.e. a 0-5 Amp ammeter.

...read more.

This student written piece of work is one of many that can be found in our GCSE Electricity and Magnetism section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related GCSE Electricity and Magnetism essays

  1. Marked by a teacher

    Draw stress and strain graphs for the metal copper and the alloy constantan. Calculate ...

    4 star(s)

    3. Record the measurements of wire length and diameter. Then work out cross-sectional area of the wire by halving diameter to get the radius of each wire and then put in to the formula ? r�, to obtain the cross-sectional area of the wire. 4. I will place the meter rule on the table, using sellotape to keep it steady.

  2. Physics Coursework Gravity Investigation

    were parallel to the floor, perpendicular to the stand and pointed away from the bench. 2. The first rule was obtained and attached vertically to the lower clamp at approximately a height of 50cm. Once the rule was inserted into the clamp, the clamp was tightened.

  1. Resistance Coursework

    * 100cm wire: to experiment on. * 1 ammeter: to measure the current in the circuit. * 1 voltmeter: to measure the voltage in the circuit. * Connecting wires: to join up the devices and make a complete circuit. * Crocodile clips: to connect the wires to the devices.

  2. Investigating the resistivity of constantan

    This should compensate for any variations in thickness along the wire. I will also use the same equipment throughout my experiment. I will make sure the wire is straight and exactly 1m long when I stick it down onto the ruler. I preferred using digital multimeters instead of analogue meters.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work