GCSE Physics coursework

How the length affects the resistance in the wire.

Plan:

• Introduction

• Aim

• Equipment

• Controlled variables

• Accuracy

• Theory

• Prediction

• Method

• Results (Results table and graph)

• Analysis

• Further investigations

• Evaluation

Introduction

The purpose of this investigation is to expose the factors responsible for affecting the resistance of a wire in an electrical circuit. Many factors will have to be investigated before I start a real experiment. Resistance occurs when there’s a substance, which can resist the flow of electricity which goes through it.

Resistance depends on many factors, such as:

• Type of the material

• Its temperature

• Dimensions, and thermal properties

• The surface

• Frequency and magnitude of the current.

Aim

The aim of this experiment is to investigate how the length affects the resistance in the wire. I will be measuring the voltage and current, which are going to go through the wire. According to the results I get, I will be calculating the resistance of the wire. Whilst varying the length of the wire, I will be recording all the changes, which occur in the wire. After that, I will be able to plot the graph and investigate how the length affects the resistance in the wire. Although, I will be measuring the resistance in the wire and investigating the factors, which affect it, I also need to produce reliable evidence, which will prove my prediction was right. In order to prove it, I will need to link my evidence to the scientific knowledge. In my particular experiment it is going to be the Ohm’s Law, which basically says, that the current passing through a wire at constant temperature is proportional to the potential difference between its ends. Therefore, I will be investigating and trying to prove that this law relates to my particular experiment.

Also, in my particular experiment I’m not going to control all the variables, such as temperature of the wire, dimensions, thermal properties, magnitude of the current and etc. Of course there are some reasons for that. It is very difficult to measure some of these variables, and they also don’t relate to the question and aim of my experiment. In my experiment there will be following controlled variables, which I will be controlling and changing during the experiment.

Controlled variables:

• Type of the material (Types of the wire)

• The supplied voltage (will be hopefully kept the same during the whole experiment)

• Thickness of the wire (SWG)

Equipment:

• Ruler (100cm)

• Piece of Nickel Chrome wire 60cm long (this particular type of wire will be constantly used only in the real experiment)

• Scissors

• Battery Power Supply

• Voltmeter

• Ammeter

• Crocodile clips

• Calculator

Accuracy:

First of all, I’m going to keep a fair test. Therefore, I’m going to make sure I use the same material, thickness, and type of the wire during the whole experiment. Of course, in my trial experiment I’m going to change the thickness, length, and type of the material, in order to choose the best type of the material, thickness, and optimal range of lengths for my real experiment. In order to keep my experiment as accurate as possible, I’m also going to use a battery as a power supply instead of connecting the equipment into the plug and using normal electricity. I think that plugging the equipment in and using normal electricity is not very accurate, because some electric faults might happen, causing the decrease, increase or even a cut in the electricity. As a result this might affect the results in my experiment. Therefore, I’m going to use a battery as a power supply. While I’m setting up the circuit, I’m going to switch the power off. I’m also going to make sure there will be no risk for me and the other students, by using the crocodile clips very accurately and making sure, that while using, the wire doesn’t attract with the other subjects and materials. When I find out the optimal length of the wire, I will cut the wire. For example, if the optimal length of the wire is 55cm, I will cut 60 cm, in order to make sure I put the crocodile clips exactly at two points, 0 and 55. In my experiment I’m going to work in pair with another student. So, while he is taking the records, I will be measuring holding the wire straight, so it doesn’t attract with anything else. While taking the records, we are also going to be accurate, by using 0.00 measuring scheme, rather than 0.0, which is not as accurate as the first one. I will be measuring the results using a voltmeter and ammeter. There’s a reason why I think the voltmeter should also be used. The voltage supplied by the power pack cannot be regarded as a very accurate one. Therefore, I’m going to use voltmeter. Using of a voltmeter and ammeter will help me to measure the resistance accurately. After my partner and I finish taking the readings, I’m going to put them in the results table. In order to get accurate results, I’m going to repeat the real experiment twice. Then, after I’ve done this, I’m going to find an average amount of resistance for each length by calculating the average resistance of the results I will get, taking into the account both experiments (both repeats of the experiment). After I’ve done this, I will be plotting two prediction graphs, which will give me an idea of what the real experiment and graph will look like. According to these results I’m going to plot a graph. A real graph will go into the analysing and evaluating section.