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

To find the resistance in a circuit when the voltage and current are known, Ohm's Law is applied. Ohm's Law states that the voltage (V) across a resistor is equal to the current (I) flowing through it multiplied by the resistance (R) of the resistor. This can be expressed in the formula:

[ R = \frac{V}{I} ]

In this case, the voltage is 90 volts and the current is 3 amperes. By substituting these values into the formula, we can calculate the resistance:

[ R = \frac{90 , \text{volts}}{3 , \text{amperes}} = 30 , \text{ohms} ]

Thus, the calculated resistance is 30 ohms. This confirms that the choice of 30 ohms is the correct answer, being the direct result of applying Ohm’s Law correctly with the provided values for voltage and current.