What happens if the series current double?
The simplest circuit I can think of is a resistor. Using Ohm’s Law, we know that the voltage V and current I are related to the resistance R
of the resistor by:
Looking at that second equation, what happens if we double the voltage, but the resistance remains the same? The current must double, too, of course.
Now let’s look at what happens to the power. The power in this circuit is given by:
Looking at this equation, we can see that if the voltage and the current both double, the power in the circuit quadruples.
In a purely resistive circuit if you double the voltage the current will also double.
The power is the product of voltage times current. If both double then the power is 4 times greater.
10 v times 5 amps = 50 VA
20 v times 10 amps = 200 VA
In a purely resistive circuit, VA and watts are the same.