Electrical resistance

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Carrie Edwards                           Electrical resistance

Electrical resistance is the slowing of a current through an electrical circuit.

The current is a word used to describe the flow of electrons, and is measured in Amps.

 Resistance happens in all electrical circuits.

 Resistant, is a property of any object or substance of resisting or opposing the flow of an electrical current.

  As a conductor conducts electricity as current, a resistor is the opposite. It slows the current down, it is another hurdle for it to pass through.

  Resistance cannot be measured directly but can be calculated from the current flowing along a wire and the voltage difference across it (potential difference)

 Resistance is then calculated using the equation:

  R = V                        Where: V =  Voltage difference across wire (volts)

         I                                       I =  Current flowing along wire  (amps)

                                                 R = Resistance of wire (ohms or     )

One way resistance can occur is through the wire. The factors that affect the resistance of a wire is;

1.Length of the wire

2.Materials of the wire

3.Temperature of the wire

4.Thickness/cross section of the wire

Length can change the amount of resistance. In a stretch of wire, collisions of electrons take place. If the length of the wire was doubled, I predict that the number of collisions would also double, therefore increasing resistance, so if the wire was half of the original size the number of collisions would be halved compared to what they were in the first place.

 

 The thickness of the wire also affects the flow of electrons and the speed at which they travel. If the wire was thin there would be many collisions amongst the electrons and they would be squeezed together, not moving freely and therefore the speed is decreased.

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 If the wire was thicker, electrons would have more space and would be free to move, therefore moving around the circuit faster.

 

  Temperature effects the electrons. Electrons are given more energy in higher temperatures (activation energy). This makes it easier for them to flow and altogether reduces resistance.

  The Material of the wire does affect resistance because different materials have different structures, some structures will increase resistance but some others have impurities, which decrease conductivity and increase resistance.

The resistance of the wire is proven by:

       R =       ...

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