What is the resistance of a circuit that draws 4 amperes from a 12-volt source?

• A. 3 ohms
• B. 4 ohms
• C. 2 ohms
• D. 1 ohm

Answer: (A)

To determine the resistance of a circuit, you can use Ohm's Law, which states that the voltage (V) across a circuit is equal to the current (I) flowing through it multiplied by the resistance (R) of the circuit. The formula can be rearranged to find resistance:

R = V / I.

In this case, you have a circuit that draws a current of 4 amperes (I) from a 12-volt (V) source. Plugging these values into the formula gives:

R = 12 volts / 4 amperes = 3 ohms.

This calculation confirms that the resistance of the circuit is indeed 3 ohms, aligning with the correct answer. Understanding this relationship between voltage, current, and resistance is essential for evaluating electrical circuits in ham radio and other applications.