Answer:
Ohm's Law
Explanation:
The Ohm's law is a relation between voltage, current and resistance:
[tex]R=\frac{V}{I}[/tex]
If you dont know the current and know the power circulating in the circuit, you can use the relation between power, voltage and resistance:
[tex]R=\frac{V^{2} }{P}[/tex]