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

I am conducting an experiment to find out how the length of wire affects resistance.

Extracts from this document...

Introduction

Science Coursework

Resistance

Introduction

I am conducting an experiment to find out how the length of wire affects resistance. The experiment I am conducting is passing an electric current through a wire made of constantan. I will take readings of the voltage and the current to find the resistance change when the length of the wire used is changed. I will be keeping the current and the voltage the same to obtain the results I want. The current will been kept unvaried by the use of a variable resistor. What I will be changing to find out about resistance is the length of the wire, 100cm – 10cm. I will work out the resistance of each experiment by use of ohms law, and I will repeat each length 3 times.

Method

To do the experiment I will first set up all the equipment (diagram below). The power pack will be set to 8volts and I will keep the current at a constant reading. To do this I will vary the variable resistor on each length change. I will connect all the equipment and turn on the electricity. I will then take a reading of the voltmeter. I will then change the length of the constantan wire by moving the crocodile clips down the wire to the length that is needed. I will then turn the power on to adjust the current flow.

...read more.

Middle

image16.pngimage17.png

image17.pngimage19.pngimage18.pngimage19.pngimage20.pngimage22.png

image23.pngimage25.pngimage24.pngimage26.pngimage04.png

image27.png

The experiment will work by electricity passing through the constantan. The length of the constantan will change the amount of resistance there is. The longer and thinner the wire is the more resistance it has because of the amount positive ions the electrons will hit as they pass through the wire. Resistance is the property of any object or substance, resisting or opposing the flow of an electrical current. The amount of resistance in an electric circuit determines the amount of current flowing in the circuit at any voltage in the circuit. They can then show the amount of electrons passing through the wire.

The resistance is found by using ‘Ohms Law’. Ohms law, named after it discoverer, Georg Ohm (a German physicist). Ohms law states that the amount of current flowing through a conductor is directly proportional to the electromotive force applied between the ends of the conductor. Resistance is defined as the ratio of the electromotive force to current, this creates the formula R= V/I, where I is the current in amps, and V is the voltage. Ohms law works in both direct current (DC) and alternating current (AC), the circuit I am using though is DC.

image35.png

The higher the voltage the more resistance that will occur due to the amount of electrons hitting the positive ions, if there are enough collisions the energy from this can make the wire become extremely hot and glow.

Resistance in wires can be shown by the diagram beneath

image28.png

...read more.

Conclusion

image42.png

The factor in the resistance which takes into account the nature of the material is the resistivity . Although it is temperature dependent, it can be used at a given temperature to calculate the resistance of a wire of given geometry.

The inverse of resistivity is called conductivity. There are contexts where the use of conductivity is more convenient.

Electrical conductivity = σ = 1/ρ


Resistivity Calculation

The electrical resistance of a wire would be expected to be greater for a longer wire, less for a wire of larger cross sectional area, and would be expected to depend upon the material out of which the wire is made (resistivity). Experimentally, the dependence upon these properties is a straightforward one for a wide range of conditions, and the resistance of a wire can be expressed as

Resistance = resistivity x length/area

image43.png

For a wire of length L = image44.pngm = image45.pngft
and area
A = image36.pngcm^2
corresponding to radius
r = image37.pngcm
and diameter
image38.pnginches for common wire gauge comparison
with resistivity =
= image39.pngx 10^image39.png ohm meters
will have resistance
R =image39.png ohms.

Enter data and then click on the quantity you wish to calculate in the active formula above. Unspecified parameters will default to values typical of 10 meters of #12 copper wire. Upon changes, the values will not be forced to be consistent until you click on the quantity you wish to calculate.

Standard wire gauges

Table of resistivities

The factor in the resistance which takes into account the nature of the material is the resistivity . Although it is temperature dependent, it can be used at a given temperature to calculate the resistance of a wire of given geometry.


www.hyperphysics.phy-astr.gsu.edu/hbase/electric/resis.html

...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

    To investigate how the resistance, R, of a length of wire, l, changes with ...

    4 star(s)

    Sometimes the metre rules have worn edges and so I will measure from 10cm instead of 0cm. I used a micrometer screw gauge to check that the diameters were correct, because this can affect the results I obtain. I took three readings for each wire, at 0m, 0.50m and 1m.

  2. An Experiment To Find the Resistivity of a Wire

    ACCURACY: - To keep this experiment as accurate as possible, I need to make sure the length of the wire is measured precisely from the inside edge of the crocodile clip, making sure that the wire is straight when I do this.

  1. An experiment to find the resistivity of nichrome

    SUPPLY 2 VOLTS AMMETER VOLTMETER WIRE METRE RULER Instead of connecting the voltmeter to the main circuit I would connect it to the wire which is being tested. I would do this so that the voltmeter is measuring the voltage of just the wire being tested and not the wires of the main circuit as well.

  2. Investigating how the length of a Wire affects its resistance.

    Although most of the points fit quite well into the line of best fit, it becomes obvious that as the resistance and length goes up, the point are further and further off the line of best fit. This can be argued to be because of many reasons.

  1. Effect of length of a conducting wire on resistance

    The thinner the wire becomes then the higher the resistance will be. If the wire is wider then the electrons can spread out as they travel down the wire, this means that there are less collisions between the metal atoms and the free-moving electrons, and the electrons can travel down

  2. Free essay

    How the length of constantan wire affects the ressistance in a electrical circuit

    If the resistance of a conductor such as a wire increases the temperature also increases. This is due to high temperature making the particles of the conductor move around more quickly increasig the chance of a collison. This is known as the collision theory, particles spread through out the conductor

  1. Investigate how length affects the resistance in a piece of constantan wire.

    Place the coil into the de-ionised water bath 4. Check that the power pack is set to 6 volts, and turn on. 5. Record the voltage and current, taking the readings off the voltmeter and ammeter respectively.

  2. To find out what happens to the efficiency of a motor as I change ...

    Starting and stopping the stopwatch at the beginning and end of each run so that the time taken for the load to be lifted could be measured. 2. Saying 'Now' to indicate to the two other people reading the ammeter and voltmeter when the values should be taken.

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