Investigate how resistance can affect the amount of current flow.

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Physics coursework.

Resistance investigation.

Introduction.

In my experiment I will investigate how resistance can affect the amount of current flow. Vibration or movement of the metal atoms causes the resistance. This means that all metals will have resistance because they all contain atoms, which vibrate.

Key factors. 

The flow of electrons along a conductor (e.g. a wire) is called a current. The size of the current flowing will depend on a number of variables. Any wire will resist the flow of electron, this is affected by:

  • Length of the wire
  • Thickness of the wire
  • Material which the wire is made of
  • Temperature of the wire

Resistance

The resistance of an object is determined by the nature of the substance of which it is composed, known as the resistivity, the dimensions of the object, and the temperature. Resistivity is expressed in terms of the ohms resistance per cubic centimeter of the substance at 20° C (68° F).

The term resistance is also used when the flow of a fluid or heat is impeded. The forces of friction provide the resistance to the flow of a fluid in a pipe, and insulation provides thermal resistance that reduces the flow of heat from a higher to a lower temperature.

Property of any object or substance to resist or oppose the flow of an electrical current. The quantity of resistance in an electric circuit determines the amount of current flowing in the circuit for any given voltage applied to the circuit, according to Ohm's law. The unit of resistance is the ohm, the amount of resistance that limits the passage of current to one ampere when a voltage of one volt is applied to it. The standard abbreviation for electric resistance is R and the symbol for ohms in electric circuits is the Greek letter omega (Ω). For certain electrical calculations it is convenient to employ the reciprocal of resistance, 1/R, which is termed conductance, G. The unit of conductance is the mho, or ohm spelled backward, and the symbol is an inverted omega.

Resistance in wires.

Physicists sometimes explain the flow of current through a material, such as a resistor, by comparing it to water flowing through a pipe. A pressure difference maintained across two ends of the pipe by a pump is like the potential difference, or voltage, across a wire maintained by a battery. The rate of flow of water, analogous to the rate of flow of charge (current), depends on the type of pipe used. A long and thin water pipe offers more resistance than a short and thick one or a pipe that has obstructions. Similarly, the resistance of a conductor is dependent upon several factors, including its length, cross section, temperature, and a property called resistivity. Resistivity is an intrinsic characteristic of the material itself defined by the voltage divided by the density of current (current per unit cross section area) flowing across the material. A material of high resistivity will require a higher electrical field to cause a given current density. If the resistivity of a material is known, as well as its dimensions, it can be used to calculate the resistance of a particular piece of material. The resistivity of a material is also dependent upon temperature.

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When a voltage, or electric potential, is applied to opposite ends of a circuit, it causes current to flow through the circuit. As the current flows, it encounters a certain amount of resistance from the conductor and any resistors in the circuit. Each material has a characteristic resistance. For example, wood is a bad conductor because it offers high resistance to the current; copper is a better conductor because it offers less resistance. In any electric circuit, the current in the entire circuit is equal to the voltage across that circuit divided by the resistance of the circuit. Resistors are ...

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