What exactly happens to an electronic device when hit by an EMP? Can it be turned on again?
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EMP sets up a voltage difference between the different sides of the device. If the voltage difference is too high, it blows out various components. (Field effect transistors are very sensitive to over voltages.) If components blow, it won’t work until repaired or replaced.
You can protect stuff by wrapping it in aluminum foil and leaning it against a metal water pipe.
All wires act like an antenna that will receive electromagnetic radiation and cause electricity on that wire. Under normal circumstances this is so small that it does not matter.
An EMP is very large amount of energy that when received by wires can cause enough electricity to disrupt or permanently damage the electronic parts.
What will happen to a device will depend upon things like strength of the EMP, distance, how sensitive that the specific parts are to over voltage, and if the device uses any form of shielding.
Most devices would be harmed by the power grid. The wires in the street will receive a lot of energy and cause power surge from the wall outlets. But even with this, what will happen to any specific device will vary.
To my understanding, generally: No. Systems vulnerable to an EMP are subjected to electrical loads in excess of what they were designed to. They burn out, kind of like a light bulb (bad analogy). Repair is unlikely, replacement is usually required.
You can also put things you might want to protect inside a faraday cage, easiest ones to get are old microwaves just make sure they aren’t plugged in.
Depends. For the device to be impacted at all, it needs to be connected to something that acts like an antenna, this can be an actual antenna, power lines, wires/traces that are part of the device itself, a cord going to a peripheral, etc.
Luckily the design choices needed to prevent a device from radiating unwanted interference work both ways, so a battery powered or unplugged device with no antennas is likely to survive without issue. The rest would depend on what kind of circuit protection is in place. The protection circuitry intended for more common events may also protect against the voltage spikes caused by EMP.
That’s not to say a device can be completely immune, as you can always have a more powerful EMP, or where there’s more energy at the frequency a sensitive part of your device happens to resonate at.
The PN junctions all open at the same time, causing a short. “Radiation Hardening” is a process by which the circuits are redesigned such that there is no path from the power supply to ground if all the switches are opened.
There are tiny wires inside tiny devices. The EMP creates a magnetic field that causes a lot of current to flow through those tiny wires. The current can either heat the wire up and burn it until it melts or create a high-enough voltage across some connected tiny device that causes it to fail.
Tiny burned out wires do not work again. Tiny burned out devices don’t work either. So, no, it can not be turned on again.
If you move a magnet along a wire, it generates electricity. An EMP is an electromagnetic pulse. It is a large, powerful magnetic field that appears and disappears very quickly. If this electromagnetic pulse passes over a wire, it will also generate electricity.
So when an EMP occurs near an electronic device, it generates electricity in every conductor inside the device. If the EMP is weak, this just disrupts the device’s operation. Imagine you have a sensor that detects 0.5V coming from a switch and triggers a motor. An EMP might induce 0.5V in the wire that goes to the sensor, even when the switch is closed. The 0.5V is literally generated *in* the wire by the magnetic field that passes over it.
If the EMP is very strong, it can generate a lot of voltage. Components inside electronic devices are only rated to handle specific amounts of voltage. Beyond that rated voltage, they fail in various ways. For example, a component called a capacitor is able to store a small amount of electric charge, kind of like a tiny rechargable battery. If you supply too much voltage, the insulation inside the capacitor will fail, and it will no longer be able to hold a charge, making it useless.
The distance between the origin of the EMP and the device matters a lot. Magnetic fields lose strength *very* quickly as you move away from the source. They follow something called the inverse square law. In order to effectively deploy an EMP, you need a *very* powerful pulse, or you need to be *very* close to the target.
I have some familiarity with electric bike systems. The motors can tolerate voltage spikes and inductance spikes, but…the controller has capacitors that will fry if they are over-volted.
The lower the voltage limit of a capacitor, the more efficient it is. Low-efficiency components run hot, so highest-possible efficiency helps the components run cooler and last longer. the common 48V controllers have 63V capacitors. Even with a safety margin, the controller can see a 70V inductance spike under certain conditions.
Have you ever wondered why the house’s breaker will trip when there is a lightning strike nearby? If you take a section of wire and pass a magnet very fast next to it, a spurt of voltage will occur, as the magnetic field pushes/pulls the electrons in the wire. A strong magnet causes a high voltage. A lightning bolt has a strong invisible magnetic field around it, and if it is near power lines, its magnetic field will add voltage to the voltage that is already in the line.
An EMP is like a lightning bolt across a large area. Any wires nearby will experience a voltage spike out of nowhere. If that voltage exceeds the limits of the components, some of them will be fried. A Faraday Cage provides a low-resistance shell with a grounding wire to give that magnetic field a matrix to convert into voltage, and a route for the voltage to flow, hopefully saving whatever is inside the cage.
So are EMPs theoretical, or do they exist now?
If they do exist, it occurs to me that they’d be solid countermeasures for nukes. Toss one up in the air at an incoming nuke and watch the rocket fall. Might fry everything within range on terra firma but beats the alternative.
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