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How does the resistivity of a constantan wire change with length
Relationship between length of constantan wire and resistance
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The Relationship Between the Length of Constantan Wires in a Circuit and the Current
Aim
To investigate the relationship between the length of constantan wires
in a circuit and the current flowing through.
Introduction
============
In a conductor electrons are able to jump between atoms. However in
insulators they remain around a single atom unable to move.
Constantan, a metal, unlike most other metals is a poor conductor
although it is also a poor insulator. Being a metal it must contain
some electrons able to move, but it will also have others, which are
unable to do so.
We are going to investigate this theory using the relationship between
the length and resistance.
Method
======
We are going to measure the current as it flows through varying
lengths of constantan. It will require an ammeter for measuring.
The variable of this experiment will be the length of constantan,
which will be decreased throughout the experiment, starting with a
metre length and gradually reducing the size with the aid of crocodile
clips. The voltage will be kept as a constant so as to make the
experiment a fair test. For a safe experiment to be completed we will
be aware of the heat produced by the electricity to prevent the wire
from overheating. To avoid this hazard we will only be using the power
supply in short periods: between lengths the power will be switched
off. So as to ensure accurate readings throughout the experiment we
will take a measurement for each length three times and find the
average.
Preliminary work will be carried out prior to the investigation so as
to establish an area in which the results can be determined
acceptable.
Diagram[IMAGE]
Prediction
==========
As the length of constantan is decreased the current will increase.
This is due to the resistance on the constantan giving that it is not
a good conductor. The longer the wire the greater the resistance
resulting in a lower current.
The experiment was performed on one subject, a 20-year-old female gymnast that weighed approximately 58.6kg. First, she performed the test with the arm bike, which had 3 stages of 25Watts, 50W, and 75W all lasting 3min each. Before the end of
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[IMAGE] Most reactive Potassium Sodium Lithium Calcium Magnesium Aluminium Zinc Iron Tin Lead Copper ------ Silver Gold Potassium Least reactive Electrical flow through metals work like this: the current in the metal is carried by electrons and will only flow if there charges which can move freely.
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F Another wire, or exact same properties (Nickel Chrome, thickness 34). mm and length 30cm) was placed on top of the previous wire, in the same position, both straight and flat. F. The power was turned on again and the same procedure was repeated. recording current and voltage at three points on the variable. resistor.
There fore less current passes through with the same voltage. Simply it is how hard it is for the electrons to pass through the wire. Temperature: When the metal wire is heated , more energy s given to the atoms, therefore they vibrate more. From this there is a greater chance of collisions with the electrons and they are impeded more, therefore less charge is passed by the electrons and the resulting current is reduced. This means while conducting the experiment the temperature of the wire must be kept constant to maintain a safe and fair test.
-Voltmeter -Variable resistor -Power Supply -Various diameters of wire -Crocodile clips -Metre ruler [ IMAGE] Diagram:.. Secondary Source - (Obtained in A-level PHYSICS by Roger Muncaster). Page 536 - "The 'Page The electrical resistivity of a material is defined by R = L / A Where R = Resistance of some conductor(Î).
Basic Mathematics for Electronics seventh edition: Nelson M. Cooke, Herbert F.R Adams, Peter B. Dell, T. Adair Moore; Copyright 1960
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