Final answer:
Without information on the circuit arrangement or current, the specific potential drop across the 30-Ω resistor cannot be found; more details are required to apply Ohm's law.
Step-by-step explanation:
To determine the potential drop across the 30-Ω resistor in a circuit with a total voltage of 30 V, we need to apply Ohm's law. Ohm's law states that the voltage drop (V) across a resistor in a circuit is equal to the current (I) flowing through it multiplied by the resistor's resistance (R), formulated as V = IR. However, without information on whether the resistors are in series or parallel, or the value of the current, we cannot provide a specific answer to the question posed.
If the resistors are in series, the current through all resistors would be the same, and the voltage drop across each can be found by multiplying that current by the resistance of each resistor. If the resistors are in parallel, the voltage drop across each would be the total voltage applied to the circuit. In either case, we need the current or the arrangement of the resistors to calculate the exact potential drop across the 30-Ω resistor.