BENGUET STATE UNIVERSITY
COLLEGE OF ENGINEERING
DEPARTMENT OF ELECTRICAL ENGINEERING
ABE 152 ABE ELECTRIFICATION AND CONTROL SYSTEMS
MODULE 3: RESISTANCE, INDUCTANCE, AND CAPACITANCE IN AC CIRCUITS
Resistance, inductance, and capacitance are fundamental elements that play significant roles in
shaping the performance of electrical and electronic circuits. Each of these components exhibits
unique electrical characteristics, and when combined, they create complex systems that power
everything from household appliances to advanced technology. In this module, we will explore the
basic concepts of resistance, inductance, and capacitance circuits, highlighting their fundamental
properties, symbols, and key equations. By the end of this module, you will have a foundational
understanding of these essential circuit elements and how they interact in electronic systems.
RESISTANCE
Resistance is a fundamental property of a material that describes its opposition to the flow of
electric current. It is typically measured in ohms (Ω) and is represented by the symbol 'R'. Materials
with high resistance impede the flow of electrons, while materials with low resistance allow
electrons to flow more easily.
Resistance finds applications in numerous electronic devices and circuits, such as voltage dividers,
current limiting, and heating elements in appliances.
INDUCTANCE
Inductance is a property of a coil or wire that describes its ability to store energy in a magnetic field
when an electric current flows through it. It is measured in henrys (H) and is represented by the
symbol 'L'. Inductors resist changes in current flow.
Self-inductance refers to the ability of an inductor to induce a voltage in itself when the current
changes. Mutual inductance is the interaction between two inductors that induces a voltage in one
coil due to the changing current in the other coil.
Inductors are essential in various electronic circuits, including power supplies, filters, and
transformers.
Inductive reactance (�� ) is the opposition that an inductor presents to alternating current (AC). It
depends on the frequency of the AC signal and the inductance of the coil.
CAPACITANCE
Capacitance is a property of a capacitor that describes its ability to store electrical energy in an
electric field between its plates when a voltage is applied. It is measured in farads (F) and is
represented by the symbol 'C'. Capacitors resist changes in voltage. Capacitors can store and release
energy in electronic circuits, making them essential in applications like timing circuits, signal filtering,
and energy storage.
Capacitive reactance ( �� ) is the opposition that a capacitor presents to AC. It depends on the
frequency of the AC signal and the capacitance of the capacitor.
RLC CIRCUITS
In practice, circuits often contain combinations of resistors, inductors, and capacitors.
Understanding how these components interact in series (RLC circuits) and parallel (RLC circuits)
configurations is crucial for designing and analyzing complex circuits.
1. The behavior of a pure resistor in an AC circuit is exactly similar to that in a DC circuit. The laws
governing resistors in DC systems may therefore be applied to AC circuits, assuming that RMS
values of voltage and current are used.
���� =
����
�� ��
= ���� ����
2
= 2 � (���� ���� )
Where: ���� = ������� ����� ��������� �� �ℎ� ��������
���� = ������� ����� ��������� �� �ℎ� ��������
2. A pure inductor in an AC circuit takes a current that lags behind the impressed emf by exactly 90
electrical degrees. Storing and releasing equal amounts of electromagnetic energy during successive
quarter cycles, the average energy per cycle involved in such circuit is zero; this means that the
average power delivered to an inductor is zero.
In an AC circuit containing pure inductance the following formula applies:
3. A perfect capacitor in an AC circuit takes a current that leads the impressed emf by exactly 90n
electrical degrees. Storing and releasing equal amounts of electrostatic energy during successive
quarter cycles, the average energy per cycle involved in such circuit is zero; this means that the
average power delivered to a capacitor is zero.