# Calculating Current from a Function Generator

1. May 9, 2012

### Student1008

I wasn't sure where to post this, but I am a physics student working on a thesis and the experiment I ran involved using a function generator to generate a magnetic field (wire was bent into a loop). I am trying to figure out how to convert the frequency (15 MHz) and Vpp (10V) to current so I can calculate the B-field. I know it's not as simple as V = IR since it's a wave (pulse bursts to be exact). Please help!

2. May 9, 2012

### sophiecentaur

Hi
If you want to measure the current through a coil then you can put a small Resistor in series (at the Earthy End would be easiest) and look at the volts across that. The current through your coil will then be I=V/R. If the current is really high then your resistor can be very low and still give you a measurable voltage drop across the resistor. This is just what a DVM does, in fact, when measuring current.
The high frequency involved could be a problem here, though, if the coil has multiple turns and could be self-resonant. This can be detected by varying the frequency and checking that the current is just dropping linearly from 0 to 15MHz - i.e you are off resonance. It would dip sharply at a parallel resonance.

3. May 9, 2012

### Student1008

Is this the only way to measure the current? I was also thinking of trying to formulate a wave equation from the frequency/B-field (I am studying magnetoinductive waves). Would you have an idea of how to do that?

4. May 9, 2012

### DragonPetter

You can also use a hall sensor to measure current, assuming your test setup is still in place.