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Coursework for physics - resistance of a wire

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Introduction

Investigationimage00.png

Resistance of a wire

Introduction:

In this investigation we will aim to find how the resistance in a wire affects the resistance in a circuit, by firstly changing the type of wire we use and then, in the main test to see how the length of the wire changes the resistance in an electrical circuit. In the pre-test the variable is the type of wire which we used, we used this information to see what wire to use in our main test. In the main we changed the length of a wire to see how the length of the wire will change the resistance in the current.

Hypothesis:

In our investigation we will see how changing the type of wire and the length of wire this affects the resistance for electrons flowing through the circuit. As electrons enter the wire they collide with ions which are a form of resistance. As these electrons move along, and the particles collide, other electrons leave the wire at the other end, as the electrons are pushed out. When you change the type of wire you are changing how the electrons will flow in the circuit, as the different lengths and types of wires have different atoms and

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Middle

Main test

Ohm's Law defines the relationships between (P) power, (E) voltage, (I) current, and (R) resistance. One ohm is the resistance value through which one volt will maintain a current of one ampere.

(I)
Current is what flows on a wire or conductor like water flowing down a river. Current flows from negative to positive on the surface of a conductor. Current is measured in (A) amperes or amps.

(E)
Voltage is the difference in electrical potential between two points in a circuit. It's the push or pressure behind current flow through a circuit, and is measured in (V) volts.

(R)
Resistance determines how much current will flow through a component. Resistors are used to control voltage and current levels. A very high resistance allows a small amount of current to flow. A very low resistance allows a large amount of current to flow. Resistance is measured in image04.pngohms.

(P)
Power is the amount of current times the voltage level at a given point measured in wattage or watts.

Equipment

  • Battery pack-This will be used to supply power to the circuit
  • Leads-These connect up components in the circuit
  • Constantan wire-This is our test wire and is our independent variable with different lengths
  • Volt meter-This measures the volts in the circuit
  • Ammeter-This measures the amps in the circuit
  • Meter ruler-Used to measure length of wire used
  • Invariable resister-used to allow our charge to be the same in each experiment
  • Crocodile clips-to attach the independent variable to the circuit

Method

  1. Collect equipment
  2. Attach Constantan wire to a meter ruler
  3. Set circuit up as shown above
  4. Turn battery pack on
  5. Adjust the rheostat to give a current of 0.28amps
  6. Attach crocodile clips to where you want to the measure
  7. Measure the voltage for each different length in 10’s
  8. Repeat for all measurements up until 100cm three times

Scientific explanation for main test

Resistance of a wire depends on several factors:

  • Material,
  • Length,
  • Thickness,
  • Temperature.
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Conclusion

Within our experiment we made some mistakes, these may have affected the accuracy of our experiment and the reliability of our conclusion. These mistakes may have affected our results and thus our conclusion; we know that our experiment was reliable and fairly accurate by looking at our graph and error bars this shows that our conclusion must be reliable and account for our experiment with great accuracy.

So overall we know that our experiment and results were of high accuracy and reliability this is confirmed by looking at our graph and averages. This also tells us that our conclusion was reliable but we also do know that we did make some small mistakes and we could have completed the experiment better if we were to do it again.

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