# Equations to Simulate Electromagnetic Field Readings

1. Aug 8, 2013

### Gibdo

I'm trying to program an application to simulate various readings of electromagnetic fields from any type of appliance or energy source. This part of physics was always my weakest. I don't remember any equations to use to get this data. The only thing I can remember is that it is related to the Inverse Square Law of some sorts. I've did many searches online, but I've seen so many different equations used, and I've tested several of them with inconclusive results. I don't know which to go by.

(I've seen some posts on here too, but I can't make sense of them. Not sure if those particular equations were what I needed)

Last edited: Aug 8, 2013
2. Aug 8, 2013

### Staff: Mentor

Your question is so vague that I don't think it is possible to give a useful answer.
The inverse square law can be interesting if you want to calculate electric potentials.

3. Aug 8, 2013

### Gibdo

To be honest, I'm not sure how to be less vague. Essentially you have electromagnetic field readers that will pick up strengths of electromagnetic fields from microwaves, clock radios, power lines, etc The output is displayed in mG or T. I just want to know the how they work, so I too can simulate that on a computer program. So if I were to read in amps and/or volts I would get a specific reading at x distance.

The field around a point charge for example, I'm assuming is E = kQ/r$^{2}$? k being the constant 9x10$^{9}$
If I = Q/t, then it would be E = k(It)/r$^{2}$? E would be N/C or V/m. But I'd need to convert to G or T after that.

Am I following this correctly? And how does this compare for appliances that are on vs off? Shouldn't we get higher readings from things that are actively running?

Last edited: Aug 8, 2013
4. Aug 8, 2013

### Staff: Mentor

Do you want to simulate the measurement of such a probe, or the electromagnetic field in some volume?

All those sources you mentioned are sources of alternating magnetic fields. To fully measure the field in one point, it is not sufficient to know the amplitude (mG or T). You also need the direction of electric and magnetic fields and the frequency (spectrum).

Sensors for (electro)magnetic fields

5. Aug 8, 2013

### Gibdo

EMF meters display an output in mG/T though, which is what I'm wanting to mimic in my computer program. I was trying study the mathematical computations those meters do to understand them better.

Last edited: Aug 8, 2013
6. Aug 8, 2013

### Staff: Mentor

Depends on the measurement device.

And what data do you have available? If you have the electromagnetic fields, just take their amplitude. Note that some devices can be sensitive to the direction of the fields, so you can get a lower measurement if you measure the "wrong" direction.

That depends on the type of measurement device you have.

7. Aug 8, 2013

### Gibdo

I don't physically own a device or have one that I'm using. But considering, we could use everyday objects, I'd have access to whatever information is printed on their labels (Amps, Volts, Frequency (Hz), and Watts)

Last edited: Aug 8, 2013
8. Aug 9, 2013

### Staff: Mentor

Everyday objects won't give you a reliable measurement of alternating electromagnetic fields.

Which labels? Do you mean the data about the power supply they need?

9. Aug 9, 2013

### Gibdo

Most appliances usually have a sticker on the inside or the side of them that lists data about the amount of Amps, Volts, or Watts that the appliance uses. I apologize, this is not my field of expertise.

10. Aug 9, 2013

### voko

Perhaps it could be easier for us to understand what you want if you gave us a complete use case of your application.

11. Aug 9, 2013

### Gibdo

Its a single axis emf meter. I want simulate this device. I have to make a program that I put in data that I can get off these labels on appliances, and get a rough estimated emf reading from said appliance. So if this A/C in the window has a sticker on it has various info, like 115 volts, 4.8 amps, 525 watt input... I could enter this data in a field, and calculate a reasonably correctly emf reading from that appliance. I really can't be any more descriptive. I'm not trying to be confusing, but I honestly don't know what else is requested here.

Last edited: Aug 9, 2013
12. Aug 9, 2013

### voko

I am afraid your objective is not achievable. Any two appliances with identical AC input requirements may have very different emission profiles.

13. Aug 9, 2013

### Gibdo

Well then, thats discouraging news to hear. Oh well, I appreciate the help none the less.