Step 1: Use the formula for electrical power.
The power \( P \) in a resistor is given by:
\[
P = I^2 R
\]
where:
- \( P = 12 \, \text{W} \),
- \( R = 24 \, \Omega \),
- \( I \) is the current.
Step 2: Solve for the current.
Rearranging the formula to solve for \( I \):
\[
I = \sqrt{\frac{P}{R}} = \sqrt{\frac{12}{24}} = \sqrt{0.5} = \sqrt{2} \, \text{A}
\]
Step 3: Conclusion.
Thus, the current through the resistor is \( \sqrt{2} \, \text{A} \), so the correct answer is (C).