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# An experiment to see how the length of a Nichrome wire Affects the resistance

Extracts from this document...

Introduction

Kaniz Naqi coursework

10NR

An experiment to see how

the length of a Nichrome wire

Affects the resistance

PLAN

Introduction:-

Resistance is a force which 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 across a electric bulb is quite thin as needs to resist the flow of particles for the bulb to glow. Resistance is measured in Ohms.

George Ohm discovered that the emf of a circuit is directly proportional to the current flowing through the circuit.

This means that if you triple one, you triple the other. He also discovered that a circuit sometimes resists the flow of electricity. He called this resistance. He then came up with a rule for working out the resistance for a circuit:

V/I = R

V- Volts

I- Current

R- Resistance

Background information

The total resistance of resistors in series is the sum of the resistance of each one. Each cm of wire has a particular resistance, if you double the length of the wire; it is like having two of the shorter wires in series.

If the small resistor represents a short wire and the large resistor is a long wire of double the length of a short one. One short wire has the resistance of 1Ohm; two short wires have the resistance of 2Ohm’s when connected in series. The long wire is just like two short wires put together.

Aim

The aim of the experiment is to see how the length of the wire affects the resistance.

How will I do this?

Brief how is the resistance of a wire affected by the length of a wire?

Middle

Finally, the length of the wire is a factor. The longer the wire, the longer it will take electrons to get to the end of the wire. This is because there will be more collisions between electrons and atoms so, in the theory, the length of the wire should be directly proportional to the resistance.

As the length doubles the resistance doubles as it is proportional.

The greater number of ions there is the longer it will take for the electrons to move through them.

50cm

100cm

I predict that as the length of the wire increases the resistance of the wire will also increase in proportion to the length. I think this is because the longer the wire the more atoms are present and so the more likely the electrons are going to collide with the atoms. So if the length is doubled the resistance should also double. This is because if the length is doubled the numbers of atoms will also double resulting in twice the number of collision slowing the electron down and increasing the resistance. Along with this the voltage will increase and the current will decrease.

Pre-test results

 Length of wire (cm) Current (A) Voltage (V) Resistance(Ohms) 0 2.14 0.43 0.2 10 0.81 1.09 1.4 20 0.50 1.25 2.4 30 0.36 1.32 3.6 40 0.28 1.36 4.7 50 0.23 1.38 5.8 60 0.20 1.40 7.0 70 0.17 1.41 8.3 80 0.15 1.42 9.5 90 0.14 1.43 10.6 100 0.12 1.44 11.6

Obtaining evidence

Method

Step 1: You are given 100cm length of a Nichrome wire which has a diameter of 0.38mm. First you have to set up the equipment correctly as told.

Step 2: Once this has been done place the probes 100 apart and measure the voltage using a voltmeter.

Step 3: Then measure the current using an ammeter.

Step 4: Using both the voltmeter and the ammeter measure the voltage and current at the following ranges 90, 80, 70, 60, 50, 40, 30, 20, 10 and 0

Centimetres apart.

Step 5: Repeat this experiment 4 times and calculate the resistance at each

Length using this formula.

R = V/I

R =Resistance    V = voltage     I = Current

Conclusion

was not possible with the time allocated and was quite difficult with the temperature factor meaning results will not always be accurate.

Some other areas in the experiment that I feel that I could have improved on were factors like controlling the temperature because although it is difficult, it is a very important factor that can ruin results if not controlled. Measuring the lengths of a wire can also be an inaccuracy that could be improved, as the rulers used are not exact, and it is difficult to get an accurate reading of length by eye, as the wire might not be completely straight, it may be a different thickness throughout the length. These would have contributed as well to the error. These results would be difficult to improve on as they are reasonably accurate, and there were no anomalous results.

Nevertheless, if I were to do this experiment again, I would use newer, more accurate ammeters and voltmeters, a more accurate method of measurement, and take a much wider range of readings, and more readings so that a more accurate average can be taken.

Overall, this investigation has been a very successful one. I feel my results and analysis have been as accurate and reliable as they could have been under the time allocated circumstances. However I feel with extra time, I could have repeated the experiment and made it even more accurate and precise and adapted it to try it to other variables. These would be things like investigating the effect of cross sectional area or temperature of resistance of a wire.

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

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