In a series circuit, \( Z \) represents the **total impedance** of the circuit. Impedance (\( Z \)) is a measure of the opposition that a circuit offers to the flow of alternating current (AC) and is a complex quantity that includes both resistance and reactance.
### Components of Impedance
1. **Resistance (\( R \))**: This is the real part of impedance and is measured in ohms (Ω). It represents the opposition to current flow due to resistive elements like resistors.
2. **Reactance (\( X \))**: This is the imaginary part of impedance and is also measured in ohms (Ω). It represents the opposition to current flow due to reactive elements like inductors and capacitors. Reactance can be either:
- **Inductive Reactance (\( X_L \))**: Due to inductors. It is calculated as \( X_L = \omega L \), where \( \omega \) is the angular frequency (\( \omega = 2\pi f \)) and \( L \) is the inductance.
- **Capacitive Reactance (\( X_C \))**: Due to capacitors. It is calculated as \( X_C = \frac{1}{\omega C} \), where \( C \) is the capacitance.
### Impedance Calculation in a Series Circuit
For a series circuit with resistors, inductors, and capacitors, the total impedance \( Z \) is given by:
\[ Z = R + j(X_L - X_C) \]
where:
- \( j \) is the imaginary unit (\( \sqrt{-1} \)).
- \( X_L \) is the inductive reactance.
- \( X_C \) is the capacitive reactance.
### Example Calculation
Suppose you have a series circuit with:
- A resistor of \( 10 \, \Omega \)
- An inductor with an inductive reactance of \( 20 \, \Omega \)
- A capacitor with a capacitive reactance of \( 15 \, \Omega \)
The total impedance \( Z \) would be:
\[ Z = 10 + j(20 - 15) = 10 + j5 \, \Omega \]
This impedance can be expressed in polar form as well, where:
- **Magnitude** \( |Z| \) = \( \sqrt{R^2 + (X_L - X_C)^2} \)
- **Phase Angle** \( \theta \) = \( \tan^{-1}\left(\frac{X_L - X_C}{R}\right) \)
In this example:
- Magnitude: \( |Z| = \sqrt{10^2 + 5^2} = \sqrt{125} \approx 11.18 \, \Omega \)
- Phase Angle: \( \theta = \tan^{-1}\left(\frac{5}{10}\right) \approx 26.57^\circ \)
So, the impedance in polar form is approximately \( 11.18 \angle 26.57^\circ \, \Omega \).