Electrical ElementsR E SISTO RS, CA PACITO RS, INDUCTOR STHE PA SSI V E COMP ONE NTS

Notes for Studying

• Do not reread. Try to understand as much as you can (in your natural pace) within 25 mins. Take a five minute break, then resume for another 25 mins.

• After completing the slides, take another 5 min rest. Rest here is working your body out not coping up with social media.You recharge your brain by moving the rest of your body and you drain yourself by too much internet.

• Try to discuss what you learn with any peer (try explaining everything you learn with a ten-year-old kid.

Contents

• Electrical Elements discuss about the primary components used in electrical circuits

• It will expound on the construction and general characteristics of resistors, capacitors, inductors, and wires in a circuit.

• Common applications of these components will also be discussed

Resistors

Resistors• Provides six primary functions:

• Bias – controls the amount of voltage that will be supplied to a device (i.e. diode or BJT’s fixed bias or emitter bias)

• Voltage division – a single supply source can be divided into several lower voltages with the use of resistors

• Current limiter – resistance opposes current flow and so resistors can limit current

• Power dissipation – resistors can release power in terms of heat and some systems require such dissipations (i.e. dummy antenna); resistors cannot store energy

• Bleeder Resistor – used in power supplies to removed stored charge in a filter capacitor, which is dangerous in troubleshooting

• Impedance Matching – useful to maximize power transfer between two systems

Resistors

• Construction

• Composition type• Cheapest way of producing resistors

• Resistance value is dependent on the concentration of carbon insulating material

• Wire-wound type• Highly precise resistors and handles large power

• Not suitable for high frequencies

• Film type• Exact values can be achieved, very high precision

• More costly

• Looks similar to composition type

Carbon Composition

Wire-wound resistor

Metal Film Resistors

Mnemonics?

• Aids in remembering concepts or constants.

• Bad Boys Raped Our Young Girl But Violeta Gave Willingly. Grabe Sya No?

• Be Better Right Or Your Great Big Venture Goes West. Gold or Silver, None.

Resistors

• Potentiometer

• Handles low current at low voltages

• Usually made up of metal strip

• Adjustment is continuous

• Rheostat

• Handles large current and power

• Usually made up of wounded wire

• Adjustment is not continuous due to windingsTypes and Construction

Rheostats – they are bulky and large since they handle big power

Specifications

• Resistance value

• Type

• Wire-wound or Composition or Film

• Variable or fixed

• Wattage rating ( can be seen in the size of resistor)

• Smaller wattage rating, smaller the size

• Determines the maximum current allowable to pass the resistor without causing damage ( I2 R principle of power)

Behavior

• Resistors are typically linear in DC circuits. They obey the Ohm’s Law. Current is proportional to voltage applied.

• In AC, resistance varies with frequency. As frequency increases, resistance increases (Skin Effect). For a fixed frequency, Ohm’s law still applies.

Capacitors

Capacitors

• Used primarily to store energy in an electric field

• Impedes (or prevents) voltage changes

• Some applications include:

• Voltage multiplier

• Filter in power supply

• Coupling and bypass in amplifiers

• Bandwidth limiter

• Tuning circuits

Capacitor Basic Construction(Of course there are many variations)

Capacitor Types and Characteristics

Capacitors

• Construction

• Two metal plates with insulating dielectric in between

• Several configurations are available (mostly dependent on dielectric used):

• Ceramic

• Electrolytic

• Paper

• Air

• Tantalum (most preferred because of low loss)

Ceramic Capacitor Construction

Paper Capacitor Construction

Variable Capacitors

• There are two ways to create a variable capacitor:

• Varying distance between plates

• Varying area of the plates

Specifications• Capacitance

• Working Voltage

• Usually it depends on the dielectric material

• This will determine the maximum voltage it can effectively store; exceeding it will risk the component from being damaged

• Operating Temperature

• The allowable temperature wherein the capacitor will operate properly

• Polarization

• Some capacitors require a specific orientation in connecting voltage (i.e. electrolytic capacitors)

Specifications• Tolerance

• The range of actual capacitance values the capacitor can possibly have due to construction

• Leakage Current

• Amount of unwanted current that flows through the capacitor due to internal resistance

• Temperature Coefficient

• Amount of change in capacitance values per change in temperature

• Effective Series Resistance (ESR)

• The internal resistive value of a capacitor (resistance due to material) when used in high frequencies

Behavior

• In DC circuits, an initially uncharged capacitor will charge up to a voltage equal to the source. Once equal, it will be equivalent to an open circuit (no current flows).

• In AC circuits, a capacitor will continuously charge and discharge allowing the current flowing through it to flow without much resistance.

Inductors

• Used primarily in storing energy in a magnetic field

• Impedes the change in current

• Most common applications include:

• Transformers

• Converters

• Tuned Circuits

• Radio Frequency Chokes

Inductors

• Its basic construction is by winding a conductor

• The structure of windings affects the inductorsproperties

• Toroidal inductors (doughnut shaped) are good forshielding itself from unwanted external inductances andvice versa

• Straight inductors can be preferable in applications thanother structures

The core of an inductor is equally important. The limitations in use depends on the core.

Inductors

• The core of an inductor is where magnetic fluxconcentrates. It is analogous to the factor that willallocate the amount of space a warehouse can holdenergy.

• Air core – useful in Radio Frequency applications

• Ferrite core – useful in medium frequencies; ferrites areinsulators that behave like ferromagnetic materials

• Iron core (or ferromagnetic) – these materials are easilyattracted to a magnet; useful in low frequency (audio)applications

Specifications

• Inductance

• Current rating

• The amount of maximum current that the inductor can handle

• DC resistance

• The internal series resistance of an inductor when used in DC; at higher frequencies, this is close to infinite

Specifications

• Self-Resonant Frequency

• The frequency in which the inductor will act as purely resistive (DC resistance) because its inductance is cancelled by the inter-winding capacitance of the inductor

• Inter-winding Capacitance

• There is capacitance in inductor due to construction; two windings form two plates with air in between them serving as dielectric

• Core permeability

• It governs the inductance of an inductor due to geometry of construction

Behavior

• In DC circuits, inductors offers no large resistance (except for DC resistance). In computations, inductors in DC are equivalent to short circuit.

• Inductors blocks high frequency currents. This will be further discussed in inductive circuits.

Wires

Wires

• They interconnect components in a circuit. They offer resistance although most of the time the value is negligible.

• The American Wire Gauge is the accepted wiring standard in the Philippines.

AWG Table

AWG Table (cont)

Wires (Some applications)

• 22 AWG are the most commonly used wire in electronics circuits (non-PCB)

• 2 AWG are used as grounding wires in tall buildings or towers

• 14 AWG are commonly used in outdoor post lights

• 12 AWG are typically used for room electrical wires (towards outlets)

Review1. Which of the following is not a specification for a

capacitor?

a) Tolerance

b) Inter-winding Capacitance

c) Polarization

d) Temperature Coefficient

2. Why are wire-wound resistors not used in high frequency applications?

3. How are inductors constructed?

4. Why are different sizes available for wires?

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