In the context of electrical engineering and circuits, the term "A.C. fundamentals" typically refers to the basics of alternating current (A.C.) circuits. One important component of A.C. circuits is resistance, which is the property of a material or device to oppose the flow of electric current. Let's delve into the concept of resistance and its fundamental aspects:
Resistance (R):
Resistance is a measure of how much a material or component resists the flow of electric current. It is measured in ohms (Ω). The resistance of a material depends on factors such as its length, cross-sectional area, and the material's resistivity (a property intrinsic to the material). The relationship between these factors is described by Ohm's law:
Ohm's Law: V = I * R
Where:
V is the voltage across the component in volts (V).
I is the current flowing through the component in amperes (A).
R is the resistance of the component in ohms (Ω).
Resistors:
A resistor is an electronic component designed specifically to introduce resistance into a circuit. Resistors are used for various purposes, including voltage division, current limiting, and signal conditioning. They come in various shapes, sizes, and resistance values.
Types of Resistance Elements:
Fixed Resistors: These resistors have a specific, unchanging resistance value. They are used in many electronic circuits for different purposes.
Variable Resistors (Potentiometers and Rheostats): These resistors have a resistance that can be adjusted manually. Potentiometers are used to create variable voltage dividers, while rheostats are used to control current in a circuit.
Thermistors: These are temperature-sensitive resistors. Their resistance changes significantly with temperature, making them useful for temperature measurement and compensation circuits.
Light-Dependent Resistors (LDRs): These resistors change their resistance based on the intensity of light falling on them. They are often used in light-sensing applications.
Varistors: These are voltage-dependent resistors that have a nonlinear resistance characteristic. They are used to protect circuits from voltage surges.
Negative Temperature Coefficient (NTC) Thermistors: NTC thermistors have resistance that decreases as temperature increases. They find applications in temperature measurement and overcurrent protection.
Positive Temperature Coefficient (PTC) Thermistors: PTC thermistors have resistance that increases as temperature increases. They are used in applications like overcurrent protection and self-regulating heaters.
Understanding resistance and the various types of resistance elements is essential for designing and analyzing electrical circuits, whether they are based on direct current (D.C.) or alternating current (A.C.).