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Investigation on Transformers.

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Introduction

Rahul Bose

Investigation on Transformers

Background Information on Transformers

“Every transformer has three parts: (Physics, David Sang Chapter 21 pg 342)

  • Primary Coil – incoming voltage V1 is connected across the coil
  • Secondary Coil – this provides the voltage V2 to the external circuit
  • Iron core- this links the two coils”

The turns ratio tells us the factor by which the voltage changes:

  • A step-up transformers increases the voltage – there are more turns on the secondary than on the primary
  • A step-down transformer reduces the voltage – there are fewer turns on the secondary than on the primary.

There is a “transformer equation”, relating Vp and Vs to the number of turns on each coil, Np and Ns can be derived. The equation is Vp/Vs = Np/Ns.  This tells us that since the magnetic field in each coil is the same, it follows that the e.m.f in each coil is proportional to the number of turns in the coil. (Physics, David Sang Chapter 21 pg 342)  

How do they work?

“Transformers only work with alternating current (a.c.). The alternating current in the primary coil produces a varying magnetic field in the core. The core transports this alternating field around to the secondary coil. This induces a varying current in the secondary coil.” (Physics, David Sang Chapter 21 pg 342)  

Variables

  • Input Voltage- This is the only variable being changed in this experiment. The voltage will be altered throughout the experiment
  • Number of turns on the primary coil- This variable will be kept constant.  In my experiment the number of turns are 50.
  • Number of turns on the secondary coil- This variable will be kept constant. In my experiment the number of the turns will be 100. Therefore the ‘turn ratio’ will be 1:2.
  • The material used for the core- This variable will be kept constant. In my experiment the core is made out of Iron.
  • Separation of the wire- This variable will be kept constant as well. The secondary coil will be turned on top of the primary coil.

Equipment required for the experiment

  • 2x Voltmeter
  • Iron Rod
  • Crocodile Clips
  • Power pack
  • Coil
  • Insulation Tape
...read more.

Middle

I predict that if the input voltage increases so does the output voltage. This is because as you increase the voltage so will the current. The increase in the voltage in the primary coil will increase the magnetic field in the primary coil. This means there will be a larger magnetic field in the secondary coil. A larger magnetic field in the secondary coil means a larger voltage in the secondary coil. This is because the magnetic field changes at a faster rate which means that the e.m.f increases.

I also expect the input voltage to be directly proportional to the output voltage. This is because the transformer equation which I mentioned earlier, Vp/Vs = Np/Ns, suggest that the input voltage is directly proportional to the output voltage.  

Finally, because a step-up transformer is being used of ratio 1:2, I would expect the output voltage to be twice the value of the input voltage.

Observation

Safety Precautions

I took the appropriate safety measures to ensure my experiment went well and safely.

I was aware of the fact that it was possible to get an electric shock. There was also a possibility of burning fingers because the equipment got too hot. Consequently from the preliminary experiment we chose the range 0.0V to 1.0V. This is because the experiment could be performed safely.

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Conclusion

Predict

I predict that if the input voltage increases so does the output voltage. This is because as you increase the voltage so will the current. The increase in the voltage in the primary coil will increase the magnetic field in the primary coil. This means there will be a larger magnetic field in the secondary coil. A larger magnetic field in the secondary coil means a larger voltage in the secondary coil. This is because the magnetic field changes at a faster rate which means that the e.m.f increases.

I also expect the input voltage to be directly proportional to the output voltage. This is because the transformer equation which I mentioned earlier, Vp/Vs = Np/Ns, suggest that the input voltage is directly proportional to the output voltage.  

Finally, because a step-up transformer is being used of ratio 1:1, I would expect the output voltage to be the same as the input voltage.

...read more.

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