AC1 Fundamentals Unit 7 – Capacitive Reactance
Exercise 2 – Series RC Circuits
EXERCISE OBJECTIVE
When you have completed this exercise, you will be able to determine characteristics of series
RC circuits by using calculated and measured values. You will verify your results with an
oscilloscope.
EXERCISE DISCUSSION
- Capacitive reactance, like resistance, increases as the number of series capacitors increases.
The total capacitive reactance is the sum of the individual reactances. - Capacitive reactance increases result in lower circuit current and higher circuit impedance.
- The current in a series circuit flows through each series component.
- The total opposition to current flow is impedance (Z); it is measured in ohms.
- Total impedance is found with this formula: Z = sqrt(R^2 + X^2 C)
- Impedance is a phasor; the total resistance lies on the x-axis and the total active reactance lies
on the y-axis. - In RC circuits the applied voltage equals the square root of the sum of the squares of the
voltage drops. - The phase angle of the circuit impedance is found with this equation:
θ = arctan (XCT/RT)