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Perhaps I'm not thinking about this correctly, but I've never understood if there is really a distinction between voltage and current being harmful to an electronic device of any kind. Obviously, current is the the actual moving electrons which we know can transfer energy in the form of heat which can be dangerous in large amounts. Voltage on the other hand, is just a potential difference, but the force that causes current. So yes, without a voltage there would be no current; but if we could apply a voltage across some electronic device and stop all current, the device would be fine no? Isn't it ultimately the current that causes damage or can destroy some electronic device?

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Obviously, current is the the actual moving electrons which we know can transfer energy in the form of heat which can be dangerous in large amounts.

Fair enough, but forget about electrons. Just deal with the concept of current.

Voltage on the other hand, is just a potential difference, but the force that causes current.

Correct.

So yes, without a voltage there would be no current; but if we could apply a voltage across some electronic device and stop all current, the device would be fine no?

You have described a switch.

enter image description here

Figure 1. Knife switch (as used by Dr. Frankenstein, et al.). Credit AYL.

Isn't it ultimately the current that causes damage or can destroy some electronic device?

Not always. Insulation breakdown can occur when too high a voltage is applied. This could be, for example, the insulation on copper windings (the clear varnish type) or the insulation between the gate and substrate on an FET transistor. On the former the insulation breakdown will be followed by a short-circuit which will lead to high currents and burn-out. In the latter the device just won't operate and you may not even smell the smoke.

Note, you might see insulation breakdown rated in kV/mm. Roughly speaking, if I had a 100 V rated cable and an insulator of 5 kV/mm then I would need 0.02 mm of insulation. In practice we have to allow for stretching, minor damage, tolerances, etc., so the result may be quite a lot thicker.

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  • \$\begingroup\$ Can you possibly explain how that is though? So if voltage is just this potential difference, what is physically happening that causes this insulation breakdown you described? Unlike current, I'm having trouble understanding what too high of a voltage really means, or the physics behind how this can cause electronic damage. \$\endgroup\$
    – RiFF RAFF
    Oct 8, 2020 at 17:55
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    \$\begingroup\$ The molecules / atoms of the insulator are being torn apart and split into ions. Ions are charged. Moving charges are current. en.wikipedia.org/wiki/Dielectric_strength. \$\endgroup\$
    – Transistor
    Oct 8, 2020 at 18:02
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Damage is created in semiconductors when the dielectric breakdown triggers a negative resistance current breakdown. But ESD diodes are typically small and faster so only rated for 5mA so they use 2 stages of D:R impedance ratio using 10k to limit transient current and diodes limit incoming voltage thus SCR current latch up effect. SCR effects trigger with negative resistance fold back and rising current with reducing voltage, thus negative slope.

TVS protection shunts with very low Rs better but depends on source impedance of V=Q/C and ESR of source ( ESD vs lightning)

So damage is protected by impedance ratios to reduce current going in with series R to bypass diodes to Vdd,Vss or TVS to ground. Thus higher current yields higher voltage from incremental conduction of diode law but is logarithmic then cascade effects attenuate further.

also C ratio of source matters as C has some finite ESR which affects voltage transfer ratio.

So Voltage is the trigger, but follow-on current does the damage.

Power line grids use ground wire above Line then air gap arc SCR like suppressors to shunt over voltage on Line. Dual protection.

  • ground wire and tall wire antenna act as deflectors of E field to shunt bypass arc to ground.

  • then Arc suppressor air gaps shunt line voltage transients to prevent arcs down the grid to local bypass to gnd.

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  • \$\begingroup\$ I really appreciate the answer and it certainly seems like you know what your talking about, but this went way over my head. \$\endgroup\$
    – RiFF RAFF
    Oct 8, 2020 at 17:58
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In terms of protection, when we talk about voltage, the breakdown voltage or the permitted operation voltage is of interest. It means, how much voltage can be applied across the terminals of a device in steady operation, without causing the insulation to breakdown or the device to malfunction.

The current becomes relevant when power loss and increase of temperature is of interest. For example, when considering a transmission line, in most cases you have a small voltage drop across the line, while the current depends on the connected load and causes losses in the line. The thermal specifics of the line then determine how much current it can tolerate.

To summarize, there is almost always a (nonlinear) relation between voltage and current for a certain device. In some cases, it makes more sense to describe the limits of the device in terms of current (like the transmission line). You can determine a maximum allowable voltage across the line, but it's not good practice. In the case of insulation breakdown, it doesn't make sense to talk about current, since there isn't any current till you reach the breakdown voltage and the electrical discharge (current) happens. The nonlinear relation between voltage and current in this case makes the voltage a suitable criterion to describe the device's protection level.

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    \$\begingroup\$ Simple answer. Current flow does the damage. Without current flow (hence power) it's almost impossible to damage anything. To enable the current to flow (and release the magic blue smoke) an excessive voltage needs to be applied. The current then does the hard work ! \$\endgroup\$ Oct 11, 2020 at 0:33

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