Discover how the voltage is affected when the current flows through wires of varying lengths.

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Helalur Rahman Khan 3894 10.1

Ohms Law

My aim is to discover how the voltage is affected when the current flows through wires of varying lengths.

Scientific Introduction

In 1826, a German physicist George Ohm stated ‘the current in a conductor is proportional to the potential difference between its ends’, providing physical conditions like temperature stay constant. The word ‘proportional’ means that when you double the potential difference the current is also doubled automatically.

Resistance is anything in the circuit that slows the flow of electrons round the circuit. This means that if you increase the resistance then the less current will flow or more voltage will be needed to keep the same current flowing. To calculate resistance you can work it out by using the formula R=V/I. This means that resistance= voltage/ current. Resistance can be affected by temperature; if the temperature is constant then the current will be proportional to the potential difference.

Using this formula for ohms law is very important as it can find you the potential difference, current or resistance using what the circuit has. The formula is:

V (Potential Difference)=I (Current) x R (Resistance)

V=IxR

Resistance is measured using resistors, all resistors produce heat when a current flows through it. The unit resistance is measured in ohms (Ω).

An electric current is the rate of flow of charge through a surface. Current is represented by the symbol I, and its unit is the ampere (A). The current is the flow of electrons through a circuit. Current is measured by using ammeters, which are placed in series in the circuit.

The voltage or potential difference is the driving force that pushes the current around. Potential difference is abbreviated to p.d, but its symbol in formulas is V. voltage can be measured using voltmeters, which are placed parallel to the component under test.

There are four factors that affect the resistance, the first factor affecting resistance is varying the length of the wire under test, and this will affect the resistance through the wire because as the length increases there will be a higher resistance.

The second factor affecting resistance is varying the cross-sectional area; this is making the size of the component larger, this will affect resistance because it has a larger surface area for the current to flow through. This means that as the cross sectional area increases, the resistance decreases this is because there is more space in the wires for the electrons to move.

The third factor affecting resistance is changing the substance as some are better conductors and some are not. Using different materials e.g. copper or iron. Copper will have less resistance as it allows more to flow through it. This is because some materials may burn when the current is passed along through it and the atoms may vibrate more slowly along the material which will increase the resistance as the current is slowed down.

The last factor affecting resistance is the temperature, because as the temperature increases the resistance will increase. This proves that resistance is affected by temperature change.

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Hypothesis

I think that as I increase the length of the wire I will also increase its resistance. This is because if I increase the length of the wire I will be injecting more electrons into the circuit- making it harder to balance out the electrons, which means I will be slowing down the flow of electrons around a circuit. Because of this I will be decreasing the current as I increases the resistance.

The resistance of a circuit may be increased because of collisions between the electrons and the positive ions of the metal wire. The heat ...

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