AC1 Fundamentals Unit 6 – Capacitance
Exercise 1 – Capacitors
EXERCISE OBJECTIVE
When you have completed this exercise, you will be able to describe the effect a capacitor has on
dc and ac circuits by using measured values. You will verify your results with a multimeter and
an oscilloscope.
DISCUSSION
- When dc is applied to a capacitor, it begins to charge and current flows. Once fully charged,
the voltage across the capacitor is equal to the applied voltage, and the current flow stops. A
very small amount of current (leakage current) actually does “leak” through the capacitor. - A capacitor, once charged, remains at that voltage level when the applied dc is removed.
- Creating a complete circuit path between the leads of a charged capacitor will discharge it.
- When an ac source is applied to a capacitor, the signal is passed but with opposition in the
form of impedance. - The amount of impedance produced by a capacitor will depend on the capacitance and the
frequency of the applied ac signal. - When capacitance increases, impedance decreases and total circuit current increases.
- When the ac signal frequency is increased, impedance decreases and total circuit current
increases. - Capacitance affects the phase relationship between the applied voltage and current.
- The voltage across a capacitor lags the current by 90 degrees, or current through the capacitor
leads the voltage by 90 degrees.