What affects the rate of resistance in a wire?

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Physics Coursework – What affects the rate of resistance in a wire?

Aim:

I am planning to find out how a certain variable can affect resistance of a wire.

Variables:

There are a few variables, which can affect the resistance in a wire.

The thickness of the wire can affect resistance. The greater the cross-sectional area of the wire, the lower the resistance for like materials.

The length of the wire can affect resistance. The longer the wire, the greater the resistance as some of the energy is lost as heat.

The temperature can affect the resistance in a wire. The higher the temperature, the lower the resistance.

The material of which the wire is made from can affect the resistance. A poor conductor (i.e. Steel) has greater resistance than a good conductor (i.e. Gold)

Variable that I have chosen

I have chosen to investigate whether the resistance of a wire varies with changes in length.

Prediction

I believe that the resistance in the wire will increase as the length of the wire increases.

Reason

With electricity, the property that transforms electrical energy into heat energy, in opposing electrical current, is resistance. A property of the atoms of all conductors is that they have free electrons in the outer shell of their structure. All metals are conductors and have an arrangement in similar form to this:

As a result of the structure of all conductive atoms, the outer electrons are able to move about freely even in a solid. When there is a potential difference across a conductive material all of the free electrons arrange themselves in lines moving in the same direction. This forms an electrical current. Resistance is encountered when the charged particles that make up the current collide with other fixed particles in the material. As the resistance of a material increases so to must the force required to drive the same amount of current. In fact resistance, in ohms(R) is equal to the electromotive force or potential difference, in volts (V) divided by the current, in amperes (I) – Ohm’s law.

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As the length of the wire is increased the number of collisions the current carrying charged particles make with fixed particles also increases and therefore the value for the resistance of the wire becomes higher. Resistance, in ohms (R) is also equal to the resistivity of the wire, in ohm-metres (ñ) multiplied by the length, in metres (l) divided by the cross sectional area, in square metres (A).


The material and cross sectional area of the wire is constant throughout the experiment. Therefore it is clear from the formula that the resistance should be directly proportional to the length.

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