How Much Power Is Needed to Generate an EMP?

[d5ive]

Hey guys,

I am new here, first post! and have only just completed Yr12 physics so only have a basic understanding of this stuff so go easy if I'm wrong about anything.

So basically the idea of an EMP is to induce a high enough voltage in a target device/any wire in order to blow out/damage the circuitry thereby rendering the device useless. So my idea is the same as any other that has been presented to produce this effect, however I really just want to get to grips with the magnitude of power that is required to generate a change in flux large enough to produce this damage. So basically, charge up a bank of capacitors --> release in series --> pass through step down transformer --> antenna/wire/coil. That's my basic understanding of it :P

So assuming a circuit in a cell phone or other smallish device running on 3-5V let's say that I would like to produce an EMF of 6V in a wire in this device which we will speculate to be 10mm long and 2m away from source of this wave of energy. How would I calculate the required current to pass through a 1m length of wire/antenna in order to produce the necessary strength of field?

I am rather lost at the moment, playing around with EMF=BvL (assuming perpendicular to field) and EMF= change in flux/change in time and EMF=nBA2PIf etc. I really don't see how to work it out as most equations at my level of knowledge in physics tend to incorporate force in some way. I am also confused about velocity, as assuming that the target wire is stationary, then I can only see velocity being achieved from the movement of the wave produced over the wire (which is the speed of light?).
please don't go into 100% correct equations using integrals etc for correct magnetic field strength etc etc I am really chasing a basic understanding of the numbers involved and cannot be bothered :P

Thanks for any help guys, D

 

[JaredJames]

please don't go into 100% correct equations using integrals etc for correct magnetic field strength etc etc I am really chasing a basic understanding of the numbers involved and cannot be bothered :P

Firstly, if it isn't "100% correct equation" it is useless and doesn't belong here.

"cannot be bothered" - a poor attitude and if you want a basic understanding I recommend using wikipedia. People aren't going to waste their time posting for you if they don't feel you care about what they write.

I don't mean to sound too harsh, but you come here with a fairly well written question and relatively competent post overall and then finish with this rubbish at the end.

Don't assume that the subject can be reduced to anything meaningful without the "correct equations". Those equations explain the numbers.

 

[d5ive]

Hi JarednJames, I apologise for that last part of my post, I realized I shouildn't have written what I did on a forum named "Physics Forums" as physics is all about striving for the correct equation to explain everything.

Perhaps you will allow me to re write that part: Using the basic understanding of the subject that a year twelve student would have, can someone please help me understand the situation? However, now seeing you point, feel free to go into as much depth as required.

Again, apologies.

 

[berkeman]

Sorry, discussion of dangerous activities is against the PF Rules (see the link at the top of the page).

Thread closed.

 

[pmacias]

Hi D,

First of all, welcome to the community! It's great to have someone with a curiosity for science and physics here.

To answer your question, the magnitude of power required to produce an EMP depends on a few factors, including the strength of the magnetic field, the distance from the source, and the size and material of the target device. In general, the stronger the magnetic field and the closer the target device is to the source, the more damage it will cause.

One way to calculate the required current to produce the necessary strength of field is by using Faraday's law of induction, which states that the induced electromotive force (EMF) in a wire is equal to the rate of change of magnetic flux through the wire. In other words, the stronger the magnetic field and the faster it changes, the higher the induced EMF will be.

In your example, you are correct in using the equation EMF=BvL, where B is the magnetic field strength, v is the velocity of the wire, and L is the length of the wire. However, you also need to take into account the time it takes for the wave to pass through the wire, which can be calculated using the speed of light (c).

So, to calculate the required current, you would need to know the strength of the magnetic field you want to induce (6V in this case), the distance between the source and the target device (2m), and the time it takes for the wave to pass through the wire (which can be calculated using the speed of light and the length of the wire). From there, you can use Faraday's law to solve for the current needed.

I hope this helps and gives you a better understanding of the basic hypotheticals of an EMP. Keep exploring and asking questions, and you will continue to learn and understand more about this fascinating topic. Good luck!