ARRL Technician Practice Exam

If a current of 3 amperes flows through a resistor connected to 90 volts, what is the resistance of the circuit?

1. 25 ohms

2. 30 ohms

3. 20 ohms

4. 15 ohms

The correct answer is: 30 ohms

To determine the resistance in the circuit, Ohm's Law is applied, which states that voltage (V) equals current (I) multiplied by resistance (R). This relationship can be expressed with the formula: \[ R = \frac{V}{I} \] In this case, the voltage is 90 volts, and the current is 3 amperes. Substituting these values into the formula gives: \[ R = \frac{90 \, \text{volts}}{3 \, \text{amperes}} = 30 \, \text{ohms} \] Thus, the resistance of the circuit is calculated to be 30 ohms. Understanding how to utilize Ohm's Law is crucial as it applies to many electrical calculations, making it a fundamental concept in electronics and electrical engineering. The other choices represent incorrect calculations based on either misapplying Ohm's Law or misunderstanding the relationship between voltage, current, and resistance.