Inductor Voltage Calculator


Inductor voltage formula


Example Currents To Enter

This Inductor Voltage Calculator calculates the voltage across an inductor based on the inductance, L, of the inductor and the current that flows across the inductor.

The formula which calculates the inductor voltage is V= Ldi/dt, where V is the voltage across the inductor, L is the inductance of the inductor, and di/dt is the derivative of the current flowing across the inductor.

You can see according to this formula that the voltage is directly proportional to the derivative of the current. Since the derivative of a constant is equal to 0, if the current is a direct current (DC), the current across the inductor will be equal to 0. So if the current is a DC current, the current flowing through the capacitor will always be 0. This, again, is because the derivative of a constant is always equal to 0. A constant does not change. So if a user simply enters in a current such as 10A or 20A or 30A, the current will be 0, for all these values. This shows that no voltage can be across an inductor if it is connected to a DC power source. There is only voltage across an inducttor when it is connected to an AC source.

Now that this is proven by the equation, you can see that only AC power sources can have voltage across the inductor. Because the AC current is constantly changing, it is not constant. Therefore, the derivative will not be equal to 0. The di/dt value will always produce a result. Thus, the answer will not be 0. Normally, AC currents are usually sine or cosine waves. When using AC power from a source such as a wall outlet, the current is a sine wave. The wave is a cycle. It goes from low to high, low to high, low to high. It keeps changing every moment. Thus, sine or cosine waves perfectly reproduce what an AC current signal would look like.

So, when using this calculator, for the current value, the input should be a sine or cosine value, such as sin(60t), 4cos(60t), 5sin(120t), etc. These type of current values simulate actual real current signals such as those you would use in electronic circuits. Again, entering DC current values will yield a result of 0, because the derivative of a DC value is 0. Thus, current will be 0.

To use this calculator, a user enters in the current (in amperes), the inductance (in henry), and then clicks the 'Calculate' button. The resultant inductor voltage value in unit volts (V) will then be automatically computed and displayed.


What is the voltage across an inductor if the current is 6sin(60t) and the capacitance is 0.5H?

V= Ldi/dt= (0.5H)d/dt(6sin(60t))= 180sin(60t)

So the voltage across the inductor is 180sin(60t) volts (V).

What is the voltage across an inductor if the current is 5cos(120t) and the inductance is 0.2H?

V=Ldi/dt= (0.2H)d/dt(5cos(120t)= -120cos(120t)

So the voltage across the inductor is -120cos(120t) volts (V).

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