Investigating the Factors that Affect the Resistance of a Metal Conductor

Investigating the Factors that Affect the Resistance of a Metal Conductor

All metals offer some resistance to the flow of an electric current.

Several factors affect the resistance:

* Temperature

* Length

* Cross-section area

* The metal or alloy the conductor is made of

This investigation looks at the effect of length.

Background Information

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Why does resistance occur?

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Resistance occurs because the electrons in the wire have to collide to

pass on electrical current. When the electrons collide, they lose some

of their kinetic energy.

What is resistance?

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Resistance is an opposition to the flow of electrons. It is the

potential difference divided by the current.

How is resistance measured?

===========================

Resistance is measured in ohms (W) using an ohmmeter ( W ).

Ohms Law

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Resistance is worked out using the following scientific model

(Reference from Roger Muncaster's A level Physics):

r = resistivity (Wm)

l = length (cm)

A = Cross sectional area (cm )

K = Constant

R=rl

A

If r and A are fixed by choosing one

type of wire of one diameter then:

R= k x l

[IMAGE]

R l

Investigation- The affect of length on resistance

Prediction

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I think that as the length of a wire increases, so does the

resistance. Therefore, the resistance will be directly proportional. I

think this because if there is a fixed potential difference (measured

in volts) across a length of conductive material it will result in a

flow of electrons. The rate of this flow is controlled by the number

of collisions that take place between the free electrons and the atom

within the conductor. For a tiny fraction of a second, the electron

loses kinetic energy, but is instantaneously accelerated again by the

electric field.

This means that I expect a graph of R versus L to be of the form: