Measuring an electromagnet
Electrical power is calculated by multiplying volts by amps. The answer is in watts.

$$ P = VI $$

Ohm's Law says that \$ V = I R \$ so we can derive two other ways of calculating the power:

$$ P = VI = IR{R} = I^2R $$

or

$$ P = VI = V \frac {V}{R} = \frac {V^2}{R} $$



To calculate power you need to take two measurements.







simulate this circuit &ndash; Schematic created using CircuitLab

Figure 1. Current and voltage measurement.


Measure the current by connecting your meter in series with the load.
Measure the voltage across the load.


Be very careful to connect the meter leads to the right sockets and select the correct range before switching on power.