Investigating the resistance of a wire.

To investigate the variable length follow this method:

1.Place one crocodile clip at one end and fold the wire 20 cm along and clip the next crocodile clip.(SGW – 28)

2. Place in tub of water.
3. Turn the battery pack. (4 V)
4. Record the readings from the Amp metre and the Volt metre.
5. Turn the battery pack off.
6. Repeat another two times and take an average.
7. Fold the wire another 20 cm and clip with crocodile clip.
8. Repeat steps 2-6.
9. Fold the wire another 20 cm and clip with crocodile clip.

10.Repeat steps 2-6.

11.Fold the wire another 20 cm and clip with crocodile clip.

12. Repeat steps 2-6.

13. Fold the wire another 20cm and clip with crocodile clip.

14. Repeat steps 2-6.

15.Calculate the resistance for each length.

Key Factors:

There are many key factors that could affect the resistance of a wire. Some of those variables are listed below:

• The length of the wire. (Min 10 cm, max 60cm)
• The thickness of the wire.
• The temperature of the wire.
• The voltage across the circuit.
• The type of wire.

These key factors will be kept the same except for the length and thickness of the wire, which is what I will be investigating.

Fair test:

I will make this experiment I fair test by keeping many variables the same they are:

• Using the same type of wire.
• Using the same voltage across the circuit.
• Keeping the temperature of the wire the reasonably the same, that is what the tub of water is for, to put the wire in the water whilst testing the resistance.

The variables I will be changing are:

• The length of the wire.
• The thickness of the wire.

Prediction:

I predict that the thinner the wire, the higher the resistance, the thicker the wire the lower the resistance. I believe this because the thinner the wire, the less space there are for electrons to travel therefore the harder it is for the current to flow. Also the smaller the space the more chance of atoms colliding with each other which would create energy The result of this is that the energy wont be able to “spread out” as much so the resistance would be higher. The electrons are negatively charged so there would be more resistance. If the diameter of the wire was wider then more electrons could get through therefore less resistance. So the thicker the wire the lower the resistance because there is a bigger area for the electrons to travel through, so there will be less chance of them colliding into one another which means there will be less energy produced.

I predict the longer the wire the higher the resistance and the shorter wire the lower the resistance. I think this because the longer the piece of wire the further the electrons have to flow, then that would mean the more collisions with atoms, which would increase the energy therefore increasing the resistance.  Also if I double the length then I double the resistance. The electrons start of with kinetic energy they then collide with other electrons, which is then transferred to heat energy.

I think that the shorter the wire the lower the resistance because they have less of a way to travel which means they wont collide with as much atoms, therefore less energy will be produced.

Background Info:

Resistance opposes the flow of an electric current around a circuit so that energy is required to push the charged particles around the circuit. The circuit itself can resist the flow of particles if the wires are either very thin or very long. E.g. The filament of an electric light bulb.

Ohms law:

He discovered relationship that the amount of steady current through a large number of materials is directly proportional to the potential difference, or voltage, across the materials. Therefore of the voltage (V)(in units of volts) between two ends of a wire made from one of these materials is tripled, the current (I)(amperes) also triples; and the quotient V/I remains constant. The quotient V/I for a given piece of material is called its resistance, R, measured in units name ohms.

Safety Factors:

The safety factor I need to consider when doing this investigation are:

• The length (it cant be to short)
• The width (it cant be to wide)
• The voltage (it cant be to high)
• Mixing water with electricity (it can be dangerous)

If I come across any of these safety factors I will:

• Increase the length.
• Decrease the width.
• Decrease the voltage.

Method:

Set up the circuit shown below:

• I will be testing five different lengths of wire; 10cm, 15cm, 20cm, 25 cm and 30cm. (SGW –28)
• Clip the crocodile clips, one at one end of the wire and the other at the other end of the wire.
• Place in tub of water.
• Turn the battery pack on. (4V)
• Record the readings from the Amp metre and the volt metre.
• Repeat another two times and take an average.
• Do this for each length of wire and work out the resistance for each length. Resistance = voltage

                                     Current.

Equipment:

• 60 cm piece of Nickel Chrome wire.
• An amp metre (0-5)
• A volt metre (0-15)
• 0-12v-battery pack.
• Crocodile clips.

Range:

I will be looking at five different lengths ranging from 10 cm- 30 cm.  I will be looking at five different widths of wire.

Problems:

The problems I found whilst undergoing this investigation is that we used different SGW. We also found that we needed to decrease the voltage from 6V-4V.

Results:

Observations