The Characteristic Curve


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Perhaps you remember that we can find out the electrical power P if we know amperage I and voltage U:

P = U ⋅ I

If you have the U-I-curve, you can determine the electrical power for whatever amperage-voltage-pair you like.

Example 1: Which power will a light bulb transform at a voltage of 3 V?
First you have to find out which amperage belongs to the voltage of 3 V. The diagram shows you that the amperage is about 0,5 A.
Then you use these values for voltage and amperage and plug them into the formula for the electrical power:

P = U ⋅ I
P = 3 V ⋅ 0,5 A
P = 1,5 W

The power of this light bulb is therefore 1,5 W if it is operated at 3 V and 0,5 A.

What would the light bulb's power be if we operated it at 6V or even at 9V?