Distance relationship between primary/secondary coils

[tima89]

We have done a simple experiment on AC transformers.
Given: AC Supply. Big primary coil. Smaller secondary coil. Even smaller metal rod. (They all fit into each other) Voltmeter
What we did:
Connected AC supply to the primary coil. Voltage kept constant at all times
Secondary coil was placed in the primary coil, and connected to a voltmeter.
procedure:
Secondary coil was raised X distance from the primary coil. (Measured top to top).
Voltage on the secondary coil measured with each step.

Now, our results (Voltage vs. Distance) showed parts of a sin (or cosine) graph, and we are having a hard time justifying it. (i know that flux is BAcos(theta)
I would be very pleased if someone could explain it.

Thanks in advance

 

[berkeman]

What equation should govern the pickup voltage as a function of distance? What equation describes the 3-D shape and intensity of the magnetic field created by a wire loop?

 

[kyle8921]

I would first like to commend you on conducting a simple experiment on AC transformers. It is important to understand the principles behind these devices as they are widely used in various applications.

Now, let's discuss the distance relationship between the primary and secondary coils. The results you obtained, showing a part of a sine or cosine graph, can be explained by the principle of electromagnetic induction. This principle states that when a changing magnetic field passes through a conductor, it induces a voltage in that conductor.

In your experiment, the AC supply passing through the primary coil creates a changing magnetic field. As the secondary coil is placed inside the primary coil, it is exposed to this changing magnetic field, which induces a voltage in the secondary coil. This voltage is measured by the voltmeter.

Now, as the secondary coil is moved away from the primary coil, the strength of the changing magnetic field decreases. This results in a decrease in the induced voltage in the secondary coil, which is reflected in your results as a decrease in voltage with increasing distance.

The fact that your results show a part of a sine or cosine graph can be explained by the equation you mentioned, which is the formula for calculating the flux (magnetic field) passing through a conductor at an angle (theta). As the secondary coil is moved away from the primary coil, the angle (theta) between the two coils increases, resulting in a decrease in the flux passing through the secondary coil.

In conclusion, your experiment has successfully demonstrated the principle of electromagnetic induction and the relationship between the distance of the primary and secondary coils and the induced voltage. I hope this explanation helps to clarify your results and the justification behind them.