D

Step 1: Understand the context of the question. We are looking for a law that relates to the heat produced in a resistor due to electric current.
Step 2: Analyze the options provided:
- Option A: Faraday’s Law relates to the amount of substance altered at an electrode during electrolysis. It does not pertain to heat produced in resistors.
- Option B: Kirchhoff’s Laws pertain to current and voltage in electrical circuits but do not directly relate to heat production in resistors.
- Option C: Laplace’s Law is related to pressure in fluids and is not relevant here.
- Option D: Joule’s Law states that the heat produced (Q) in a resistor is directly proportional to the square of the current (I) flowing through it and the resistance (R) of the resistor over time (t):
$$ Q = I^2 R t $$
Step 3: Conclude that Joule’s Law is the correct law for calculating heat in a resistor.
Therefore, the correct answer is D.