Investigating the Factors that Affect the Resistance of a Wire
Aim
To study the factors which affect the resistance of a wire.
Background Information
Although current and potential difference measure different things,
they are related to each other. In 1826, Georg Ohm discovered that
doubling the p.d. doubled the current. (Taken from
Ohm's Law: the current flowing through a metal wire is proportional to
the potential difference across it (providing the temperature is
constant).
Electricity flows through a conductor, in this case the wire, by means
of free electrons. The number of free electrons varies depending on
the material and the more free electrons, the better the conductor as
there is less resistance. The free electrons collide with atoms and
gain some of their energy. As a result, the electrons collide with
other electrons across the length of the wire causing electricity to
be conducted.
Resistance is the result of energy loss as heat. It is caused by
collisions between the free electrons and metal atoms. These
collisions convert some of the energy that the free electrons are
carrying into heat. This is why a wire can get hot when a current
flows through it. Also, when a metal is hot, the atoms vibrate more,
getting in the way of the electrons trying to move passed them causing
a higher resistance.
The resistance of a length of wire is calculated by measuring the
current present in the circuit (in series) and the voltage across the
wire (in parallel). The following formula is then applied:
V (voltage) = I (current) x R (resistance)
OR
[IMAGE]R = V
I
Preliminary Work
In the preliminary work we had to choose and investigate one of the
four main factors that affect resistance. These are:
· Temperature
· Thickness of the wire
· Material of wire
· Length of wire
I decided to test how the length of wire affects the resistance.
During the preliminary work, I tested the method that I would use for
From this I can tell I can use 3 volts and resistance wire that is
equation V = IR. V - volts, I - current and R - resistance. I plotted
I also decided to use a wooden block to keep hold of the wire, because
It happens when particles make effective collisions with sufficient energy. The sand is Apparatus = == == =
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.
of the atoms, so if there are more or larger atoms then there must be
Factors Affecting the Resistance of a Wire The aim of this experiment is to investigate one factor that affect the resistance of a wire. I will do this by performing an experiment. First I will need to identify the factors that effect resistance. There are a few factors that affect the resistance, it is determined by the properties an object has.
-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).
The invisible bits of negatively charged matter that move between objects are called electrons. The words electron, electricity, and electronics all come from the Greek word for amber – elektron. The transfer of electrons explains the electric force that attracts the balloon to the wool. Rubbing the neutral balloon with the wool cloth allows some electrons to leave the wool and stick to the balloon.
First off, what is current. Current is expressed in a unit called Amps. Amps are a measurement of how many electrons pass per second. That is to say, a wire with 40 coulombs passing any point in a 2 seconds would be said to have 20 Amps of current (40 Coulombs (a unit of charge given as 6.24x1018 electrons) / time in seconds or in this case, 2 seconds. The Amp is also known as Coulombs per second) Another trick about current is that it is measured in the movement of the positive charge. Literally that is to say the current moves in oppostion to the electrons. This is because originally it was thought that the positive charge is what moved, both are viable, but in reality a positive charge is generally fixed since within an atom the electrons are migratory, while the protons and neutrons tend to be stationary.
This obviously increases the number of collisions, too.. [ IMAGE] Faster collisions increase the rate of reaction. High temperatures also increase the energy of the collision, because it makes all the particles move faster. Faster collisions are only caused by increasing the temperature. Reactions only happen if the particles collide with enough energy.
In 1750, Benjamin Franklin wanted to prove that lightning was caused by electricity. He tested his theory with an experiment in which he flew a kite with a metal key attached to it into a storm cloud. The historical facts are not clear as to if he actually carried out the experiment, which is why there is doubt that he is the discoverer of electricity. But, we still credit him with the idea. He also did other experiments concerning electricity, but others after him would have to ...
The phenomenon called electromagnetic induction was first noticed and investigated by Michael Faraday, in 1831. Electromagnetic induction is the production of an electromotive force (emf) in a conductor as a result of a changing magnetic field about the conductor and is a very important concept. Faraday discovered that, whenever the magnetic field about an electromagnet was made to grow and collapse by closing and opening the electric circuit of which it was a part, an electric current could be detected in a separate conductor nearby. Faraday also investigated the possibility that a current could be produced by a magnetic field being placed near a coiled wire. Just placing the magnet near the wire could not produce a current. Faraday discovered that a current could be produced in this situation only if the magnet had some velocity. The magnet could be moved in either a positive or negative direction but had to be in motion to produce any current in the wire. The current in the coil is called an induced current, because the current is brought about (or “induced”) by a changing magnetic field (Cutnell and Johnson 705). The induced current is sustained by an emf. Since a source of emf is always needed to produce a current, the coil itself behaves as if it were a source of emf. The emf is known as an induced emf. Thus, a changing magnetic field induces an emf in the coil, and the emf leads to an induced current (705). He also found that moving a conductor near a stationary permanent magnet caused a current to flow in the wire as long as it was moving as in the magnet and coiled wire set-up.
Collisions between reacting particles are therefore more likely to occur. All this can be understood better with a full understanding of the collision theory itself: For a reaction to occur particles have to collide with each other. Only a small percentage result in a reaction. This is due to the energy barrier that is overcoming.
Faraday continued his electrical experiments. In 1832, he proved that the electricity induced from a magnet, voltaic electricity produced by a battery, and static electricity was all the same. He also did significant work in electrochemistry, stating the First and Second Laws of Electrolysis. This laid the basis for electrochemistry, another great modern industry.