Passive Components: Resistors, Variable Resistors, Capacitors, Inductors
Resistors
- Resistors are electrical devices that limit or regulate the flow of electrical current in an electronic circuit.
- They are characterised by their resistance value (measured in Ohms, Ω) which, in simplified terms, describes their ability to resist the flow of electricity.
- They follow Ohm's Law (V=IR), which states that the voltage (V) through a resistor is equal to the product of the current (I) through it and its resistance (R).
- Resistors are linear devices meaning that their voltage is directly proportional to the current.
- Fixed resistors have a defined value that cannot change. Examples include carbon film resistors or metal oxide resistors.
- Resistors can come in different power ratings, indicating how much power they can safely dissipate as heat.
Variable Resistors
- A variable resistor, also called a potentiometer, allows the resistance to be changed within a certain range.
- Variable resistors can be used to adjust current, divide voltage, or simply as a tuning component in some circuits.
- It comprises of a resistor with a sliding contact (wiper) which makes it possible to adjust the resistance.
Capacitors
- Capacitors store electrical energy in an electric field.
- They consist of two conductive plates separated by an insulator, known as the dielectric.
- The capacitance, measured in Farads (F), is the measure of a capacitor's ability to store electrical energy.
- When voltage is applied to a capacitor, an electric field is created between the plates, causing a positive charge to accumulate on one plate and a negative charge on the other.
- Capacitors block direct current (DC) and allow alternating current (AC) to pass through.
Inductors
- Inductors, also known as coils, are passive devices used in electronic circuits to store energy in a magnetic field when electric current is flowing through it.
- The unit of inductance is the Henry (H).
- They are often used in filters, sensors and transformers.
- They are characterised by their ability to resist changes in current and can block or slow down changes in voltage.
- Similar to capacitors, inductors also affect AC and DC differently. They pass direct current (DC) and can resist or block alternating current (AC) due to electromagnetic induction.