To measure resistance and verify ohms law

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PHYSICS COURSEWORK

AIM- To measure resistance and verify ohms law

SCIENTIFIC BACKGROUND

Current is the rate of flow of charge. Electrons carry the charge, which they get from the battery around a circuit. Current flows from negative to positive, even though we usually say it flows from positive to negative, as this is conventional current.

There are two types of circuit: - Series circuit.

     - Parallel circuit

A series circuit is when the electrons have only one choice of path. This circuit can have an infinite number of components as long as they are all in series. However if bulbs are included in this circuit, then the voltage is shared between them.

In parallel circuits the electrons have more than one choice of path. The current is shared in parallel circuits but the voltage stays the same.

The current is measured in amp’s (A) by an ammeter. How much energy each electron has gained from the battery, is known as voltage. Voltage is measured in volt’s (V) by a voltmeter. When voltage increases, current also increases. This is because the electrons are given more energy so they will be able to flow through the wire faster.

A resistor controls the current. There are two types of resistor:

  • Fixed and
  • Variable

A fixed resistor cannot change its value. However a variable resistor can, it is used in remote controls to alter the volume.

Resistance is measured in Ohms. The higher the resistance the more difficult it is for the electrons to flow through the wire. Resistance is affected by four factors:

  • length,
  • cross-sectional area,
  • material,
  • temperature.

A long wire will mean a higher resistance. This is because the electrons have a longer path to travel along meaning it will be more likely that the electron will collide with other particles. A shorter wire would mean a lower resistance because it will be a shorter path for the electrons to move down, resulting in fewer collisions.

A larger cross-section area would reduce the resistance, this is because there are more electrons in a thick wire. If the cross-section area was reduced there would be fewer electrons in the same length of wire, therefore increasing the resistance. A long, thin wire would have a much higher resistance then a short, fat wire.

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Different materials will have different levels of resistance. A piece of plastic would have really high resistance because it is a very poor conductor; on the other hand copper would be a really good conductor because it has low resistance. One of the reasons copper is used in wiring is because it is a good conductor.

When the temperature is increased the resistance will also increase. This is because the particles in the object will start to move around faster. This would make it harder for the electrons to flow through the wire, as there would be more collisions obstructing ...

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