The aim of this investigation is to find out how different lengths of a 1m long nichrome wire affect its resistance.

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Science Coursework/Physics

                         

AIM

The aim of this investigation is to find out how different lengths of a 1m long nichrome wire affect its resistance.

PREDICTION

I predict that if I double the length of the nichrome wire, its resistance will also double. I predict that if I half the length of the nichrome wire, the resistance will also half. Therefore I predict that resistance will increase in proportion to the increase in the length of the wire.

HYPOTHESIS

Why does a metal conduct?

A metal is made up of positive ions surrounded by a sea of free electrons. The ions in a metal are positive because it is easy for a metal to lose one or two electrons, from its outer shell, than to gain six or seven electrons to complete the outer shell. The electrons are lost and are free to move around and the ions become positive as the number of protons increase, compared to the number of electrons. The metal can now conduct electricity, as it is positive.

Here is a diagram to show the structure of a metal:

What is resistance?

Resistance is the measure of how difficult it is for the current to get through a wire.   We measure the resistance in Ohms, with the symbol

           Resistance, R = p.d. across the wire (V)___

                                       Current through the wire (I)

                                           R = V

                                               I

What causes the resistance in a wire?

The electrons in a wire are free to move through it, but it is not perfectly easy. The ions of the wire get in the way. The electrons collide with the ions and get slowed down. So a single electron will make a stop/start journey along the wire as it bumps into ions. The piece of wire has resistance because the ions restrict or resist the flow of electrons.

Ohm’s Law states that, “ The current flowing through a metal wire is proportional to the potential difference across it.” (Providing the temperature remains constant.)  ‘Proportional’ means that if you double the p.d. the current is doubled. Therefore the current is inversely proportional to the resistance. Whatever we do to the resistance, it changes the current by one over the number.

Voltage        =Current*Resistance             I.R

Resistance  =Voltage                    R  =   V                

                Current                             I

         

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Current        =___1____                       I            1 

                     Resistance                               R

This supports my prediction that if I double the length of the wire, the resistance will also double and if I half the length of the wire, the resistance will also half as I am going to change the length of a wire while carrying out this investigation.

Resistance restricts the amount of current flowing through a wire and therefore slows down any reaction, which ...

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