it states that the voltage across an inductor is V = L(di/dt), why do we not use V = IR? Or what is the derivation of V = L(di/dt) or the conceptual explanation?
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The dI/dt is the rate of change of current over time. That means current has to be changing, which only happens in an AC circuit.
In an AC circuit you have to.worry about reactance, which capacitors and inductors have (and still has units of Ohms). For a resistor, the reactance Xr = R, so Ohm’s law holds. For an inductor, the reactance is Xp = ωL, so it’s not longer Ohmic and you cant use Ohm’s law. (ω is angular frequency, and equals 2πf). It also applies to a capacitor, Xc = 1/Cω
To find the total reactance of a circuit, you would add the reactances of the resistors, inductors, and capacitors independently just like you would in any other circuit so you’re left with 3 values. One for resistors, one for inductors, and one for capacitors
You can then find the reactance of the whole circuit with X = sqrt(Xr^2 + (Xl – Xc)^2 )
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