Ham Radio General Class Practice Test

Which of the following is one effect of lead inductance in a capacitor used at VHF and above?

1. Effective capacitance may be reduced

2. Voltage rating may be reduced

3. ESR may be reduced

4. The polarity of the capacitor might become reversed

The correct answer is: Effective capacitance may be reduced

Lead inductance in capacitors, especially when used at VHF (Very High Frequency) and above, can have a significant effect on the effective capacitance. At these frequencies, the inductance associated with the leads can create a condition where the overall circuit behaves as if it has reduced capacitance—this is due to the resonant effects of the inductor (the leads) and capacitor (the capacitor itself) when combined in a high-frequency environment. As frequency increases, the impedance of the inductive lead tends to increase, which can lead to a situation where less effective capacitance is realized in the circuit. Thus, the contribution of inductance can dominate over the intended capacitance, especially if the capacitor is not designed with this in mind—resulting in degraded performance at high frequencies. In contrast, the other options involve misunderstandings of the effects of lead inductance. The voltage rating typically remains unchanged as it is more a function of the capacitor's construction and dielectric material rather than inductance. The equivalent series resistance (ESR) is influenced by factors such as the quality of materials and design rather than lead inductance alone. Lastly, the polarity of a capacitor does not change due to lead inductance; it is dictated by the