My aim is to investigate how the resistance of a piece of resistance wire depends on length and also to find the length of wire needed to make the required resistors.

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Physics Investigation (Coursework)- GCSE

Aim-

An electronics factory needs resistors of 5 ohms, 10 ohms and 15 ohms for a new electrical device. My aim is to investigate how the resistance of a piece of resistance wire depends on length and also to find the length of wire needed to make the required resistors.

Introduction-

My investigations main topic is resistance and how a length of a resistance wire affects the resistance. A selection of different wires made from constantan and nichrome will be available for me to use,

Wire A – constantan wire of approximate diameter 0.3mm

Wire B – constantan wire of approximate diameter 0.4mm

Wire C – nichrome wire of approximate diameter 0.3mm

Constantan is an alloy whose resistance stays fairly constant when it becomes hot. In fact the resistance changes by less than 0.5% even when the temperature rises by a few hundred degrees.

Nichrome, along with other metals, is an alloy whose temperature does change appreciably when it becomes hot.

Resistance-

With a given energy source, such as a battery or a generator, the size of current that flows is decided by the resistance of the circuit. All conductors resist the flow of electric charge to some extent, but some are better at it than others. The bigger the resistance of a conductor the harder it is for electric charge to flow through it. For a given voltage applied to it, the current would be less.

It is like water flowing downhill in a river. If the bed of the river is smooth the water can flow easily, and more can get through in a given time. But if the bed of the river is rocky the water can’t flow so easily. It will move downhill more slowly, and a lot of energy is wasted – you can hear the noise and see the water being thrown up in the air. You can find the same kind of effect in a conductor with a high resistance. It cuts down the flow of charge – and energy is released. The conductor gets hot. Resistance occurs when the electrons travelling along the wire collide with atoms of the wire. These collisions slow down the flow of electrons causing resistance. Resistance is a measure of how hard it is to move the electrons through the wire.

Voltage-

Voltage means when, in circuit, the voltage pushes the current away. And another name for voltage is potential difference. An instrument that is used to measure voltage is called a voltmeter, and they are measured in volts.

Current-

Current means, the amount of charge that flows in a circuit per second. An electric current is a flow of charged particles as well. Current is measured in amperes, and the instrument that we use to measure current is called ammeter.

Electricity-

Electricity means the flow of electrons that flow in one direction. And this flow on electrons can only flow in one direction in a circuit.

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Ohm’s law-

For many useful conductors there is a simple rule, which connects current, voltage and resistance. If you double the applied voltage, the current is doubled. If you halve the voltage, the current is halved. This effect doesn’t work with all conductors, but is true for metals and for carbon, if they don’t get too hot.

For most circuits we can use the rule to calculate what will happen when things change.

The rule is – The voltage across a metal resistor is proportional to the current through it, provided its temperature is constant. This ...

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