# The aim of this investigation is to see what the relationship between voltage, current and resistance is.

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Introduction

GCSE science Coursework

An investigation into the relationship:

V=I.R

September 2003

By Helen Crutcher

Bibliography

The aim of the investigation

The aim of this investigation is to see what the relationship between voltage, current and resistance is. We will be conducting two different experiments investigate Ohms law, V=I.R using, in our first experiment wire thickness as our input variable. In our second experiment, we will use wire length. In each, we will record the Voltage and current running through the circuit and use this information to work out wire resistance.

Background information

Voltage: Voltage is

Current: Current is

Resistance: Resistance isa measure of how much the current in a circuit is slowed down. Resistance is caused when electrons have to’jump’ from one It is measured in Ohms (Ω)

Ohms law

Electrons

Introduction

Hypothesis- the thicker or shorter the wire the easier it

Middle

Wire thickness | Voltage | Current | Resistance |

The gradient of this graph represents mass, so this shallow gradient shows that the mass must be large.

Evaluation of preliminary experiment

Our preliminary experiment shows us that we will be able to use this range of values for our final experiment since they gave us results that were relatively consistent with our hypothesis.

Equipment needed:

- Different lengths of Nickel Chrome (nichrome) wire(experiment two)
- Different widths of !0 cm long Nichrome wire (experiment one)
- Ammeter
- Variable resistor
- Voltmeter
- Power pack
- wires
- Crocodile clips
- Pulley

Conclusion

Analysis

Evaluation

ResistanceResistance is measured in Ohms (symbol Ω).

Resistance

The bigger the resistance, the smaller the current.

The very important equation

V = I x R

is an expression of Ohm's Law.

You MUST KNOW this equation for the exam!

If the resistance of a component is constant (stays the same)

for different values of V and I,

then a plot (graph) of V against I will be a straight line.

The gradient (slope) of the line shows how big the resistance is.

A test circuit is used to find a range of voltages and currents for a component.Components which obey Ohm's Law are Wiresand Resistors.

A component will only obey Ohm's Law at constant temperature

(meaning that the temperature must not change).In reality, an increase in current through a component

will change its temperature (the temperature usually goes up),

and so Ohm's Law is only an approximation

but it works quite well for many components.

The next page shows plots for components which don't obey Ohm's Law.

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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