Updated: Dec 9, 2025 | Source: 2022-2026 Question Pool | Topic: T7D
T7D10T7D

What reading indicates that an ohmmeter is connected across a large, discharged capacitor?

Deep Dive: T7D10

The correct answer is A: Increasing resistance with time. When an ohmmeter is connected across a large, discharged capacitor, the reading shows increasing resistance with time. This happens because the ohmmeter applies a small voltage to measure resistance, which begins charging the capacitor. As the capacitor charges, its effective resistance increases (since a charging capacitor acts like increasing resistance). Initially, the reading might be low (the capacitor appears as a short), but as it charges, the resistance reading increases. For amateur radio operators, this behavior helps identify capacitors and understand their charging characteristics.

Why Other Answers Are Wrong

Option B: Incorrect. Decreasing resistance would indicate the component is breaking down or shorting, not a charging capacitor. A charging capacitor shows increasing resistance. Option C: Incorrect. A steady full-scale reading would indicate an open circuit or very high resistance, not a charging capacitor. Capacitors show changing resistance as they charge. Option D: Incorrect. Alternating between open and short would indicate an intermittent connection or faulty component, not normal capacitor behavior.

Exam Tip

Large discharged capacitor = increasing resistance with time. Think 'C'apacitor 'C'harges = 'C'hanging (increasing) resistance. The ohmmeter's voltage charges the capacitor, causing resistance to increase as it charges.

Memory Aid

Large discharged capacitor = increasing resistance with time. Think 'C'apacitor 'C'harges = 'C'hanging (increasing) resistance. Ohmmeter voltage charges capacitor, resistance increases.

Real-World Example

You connect an ohmmeter across a large electrolytic capacitor. Initially, it reads low resistance (the capacitor appears as a short). As the ohmmeter's voltage charges the capacitor, the resistance reading gradually increases. After a few seconds, it might read very high resistance (the capacitor is charged). This behavior identifies it as a capacitor, not a resistor.

Source & Coverage

Question Pool: 2022-2026 Question Pool

Subelement: T7D

Reference: 2022-2026 Question Pool · T7 - Practical circuits

Key Concepts

Capacitor testing Ohmmeter readings Capacitor charging Component testing

Verified Content

Question from the official FCC Technician Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the T7D topic.