Method
In this experiment I intend to investigate how altering the input voltage affects the output voltage. To do this I will use a power pack with an alternating current. I will wire it up to two digital voltmeters. The first voltmeter will be attached to the primary coil. The second voltmeter will be attached to the secondary coil. Both voltmeters will be connected in parallel. The primary coil, with 50 turns, will be wound around an iron core (rod) and the secondary coil, with 100 turns will be wound over the primary coil. The transformer that I will make will be a step-up transformer.
The power supply will, then, be turned on and I will note down all the readings. The results will then be tabulated.
However before I carry out the experiment, a preliminary experiment will be performed to establish an appropriate range of volts.
Preliminary Experiment
I set up my equipment like suggested in the method. These were the results:
After doing the preliminary experiment, my real experiment will range from 0.0V to 1.0V in steps of 0.1V. The experiment worked well for these values but it didn’t for any higher volts because the iron core go to hot. The insulation began to smoke. However, from 0.0V to 1.0V, the experiment worked reasonably well and safely. The results, however, lower than expected.
Fair Test
To ensure my experiment is fair; I will set up a control. I will do the experiment as normal but I will not pass current through it. This will tell me that the variable I am testing is the only one which is affecting the output voltage. I will also keep all my variables constant except the one I am testing.
Circuit Diagram+ Actual Diagram
Prediction
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.
The table of result for the experiment
N1 = 50
N2 = 100
X = they were on top of each other (X = Distance)
Analysis
Trends of Data from the Graph
As the voltage on the primary coil increases so does the voltage in the secondary coil.
From the graph it is possible to see a degree of proportionality between the voltage in the primary coil and the secondary coil. This is also be justified by the transformer formula.
The formula Vp/Vs = Np/Ns shows that Vp is directly proportional to Vp. To use this formula, firstly, I would rearrange it to make Vs the subject. Therefore, Vs = (Ns x Vp)/Np
Now I will substitute the results of my experiment into the formula.
Vs = (100 x 0.50)/50.
Vs = 1V
However, this was not the case. In my experiment, for this particular value, I got 0.33V. This shows that my transformer is only a third efficient. This is because my graph is a straight line. The reasons for why the results are lower than expected:
- The iron core gets hot therefore electric currents are induced in the coil and core. This means there is a reduced output.
- The magnetic flux escaped through the ends of the rod.
In spite of my experiment being only a third efficient, I can definitely see my graph being directly proportional. This happens because as the voltage in the primary coil increases so does the current. As the current increases so does the magnetic field. This means there is a larger magnetic field in the secondary core. A larger magnetic field in the secondary coil suggests that it changes at a faster rate. Therefore there is a larger output voltage.
Comparing the results with my predictions
Firstly, the results showed direct proportionality. As the input voltage was increased so did the output voltage. This is what I had expected. However I had expected the output voltage to be twice the primary voltage. This was not case though. In fact, in my experiment, the output was significantly lower. The reason, however, is because the magnetic flux escaped through the ends of the rods. It escaped also because an iron core was used. Electric current was induced not only in the second coil but also in the core. This caused the core to get hot. This caused the current to be lower than expected. However, if a laminated core had been used the inefficiency would have been less.
Evaluation
Overall my experiment went well.
Accuracy
My experiment was, on the whole, very accurate. The reasons for this are:
- 2x repeats
- My pair of results had very little variation. The repeats were similar to the actual values
- The points in my graph didn’t deviate from the line of best fit. They didn’t fluctuate much
Are the results reliable?
Because 2 repeats were done and an average of that was taken, I believe my results are reliable. Although they were lower than expected, my results were consistent throughout. This can be seen in the graph which was a straight line. Although my transformer was inefficient my results were equally inefficient all the way.
Suitability of the Experiment
My experiment worked well. There were no anomalies. This shows that the method that was used was the right one. The only unsuitability was that the transformer was only a third efficient. The reasons for this were discussed in the analysis. However, this unsuitability can be improved upon.
Further Improvement
Firstly to improve my current experiment I would use the following:
- Laminated Core- Improve efficiency
- More repeats- Improve reliability + accuracy
- Ring core- To stop magnetic flux escaping as much as possible
- More accurate digital voltmeter- Improve accuracy
To extend my experiment, I will use a transformer with a turn ratio of 1:1. In this experiment, I intend to see what happens to the output voltage as I increase the input voltage.
Method
To do this I will use a power pack with an alternating current. I will wire it up to two digital voltmeters. The first voltmeter will be attached to the primary coil. The second voltmeter will be attached to the secondary coil. Both voltmeters will be connected in parallel. The primary coil, with 50 turns, will be wound around an iron core (rod) and the secondary coil, also with 50 turns will be wound over the primary coil. The power supply will, then, be turned on and I will note down all the readings. The results will then be tabulated. I am going to use the same range of volts as I did in my previous experiment. (0V – 1V in steps of 0.10V)
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.