Atomic Number – The number of protons on the nucleus.
Atomic Weight – The mass of the atom = number of protons + neutrons in the nucleus.
Valance Shell – The outer most shell of electrons.
Valence – The number of electrons in the outer shell.
Conductors – Material that contains a large number of electrons. Low resistance.
Insulators – Prevent electron flow. High resistance.
Semi-Conductors – Can act as a conductor or insulator.
Positive Ion – Positively charged atom.
Negative Ion – Negatively charged atom.
Current (I) – Movement of electrons from negatively charged atoms to positively charged atoms. Current is measured in amperes.
Coulomb (Q) –
Ampere/Amp (A) – One coulomb moving past a single point in one second.
Potential – The ability of a source to perform electrical work.
Difference in Potential – Causes electrons to flow in a circuit. Referred to as Electromotive Force (emf) or Voltage.
Voltage (V|E) – The force/pressure that moves the electrons in a circuit. Unit of measure is a volt.
Resistance (Ω) – The opposition to the flow of electrons. Measured in Ohms.
Hole – The movement of an electron from one atom to the next, creating the appearance of a + charge moving in the opposite direction.
Electron Flow – Current flowing negative to positive.
Hole Flow – Current flowing positive to negative. Electrons move in one direction, making it appear as though you have positive flow in the other direction.
Voltage Source – Supplies electrons from one end of the conductor. Removes electrons from the other end of the conductor.
Milliampere – 0.001 ampere. 1/1,000 ampere
Microampere – 0.000,001 ampere. 1/1,000,000 ampere.
Battery – Two or more cells.
Connecting cells and batteries
Parallel – Same V, more current. Lasts longer.
Voltage Rise – Potential energy or voltage introduced into a circuit.
Voltage Drop – The energy given up as electrons encounter resistance in the circuit.
Voltage rise and drop should be equal to each other. A 5v battery hooked to a radio, the radio should be consuming 5v.
Ground
Earth – Used to prevent electric shock.
Electrical – Provides a common reference point.
Resistance (R) – The opposition of electron flow (Current) in a circuit. Everything has resistance. Measured in Ohms.
Resistivity – Compares everything to silver, the best conductor.
Conductance (G) – The ability of a material to pass electrons. Measured in Mho.
Resistors – Component designed to have a certain amount of resistance. Fixed or variable.
Tolerance – The amount a resistor may vary, but still be acceptable. Varies from 1% to 20%.
Types of Resistors
Molded – Most common. Cheap. Standard resister values.
Wirewound – Used in high current circuits.
Film –
Surface Mount – Ideal for small circuit apps.
Variable – Vary linearly and logarithmically. Called a potentiometer when used to control voltage. Called a Rheostat when used to control current.
Potentiometer – Controls voltage. Has a 3rd lead on it. The 3rd arm moves and comes in contact with more/less resistive material which will vary the total resistance across points A and B.
Rheostat – Controls current. You are changing the total resistance in which changes the total current.
Resistor Identification – See color codes.
Resistors in Circuit
Parallel – Total R will always be less than the smallest value (10). If all R are the same, divide by num of resistors to get total R.
Formula 1:
Formula 2: If you have 2 resistors in parallel,
Formula 3:
All circuits consist of
Voltage Source
Load
Conductor
Switch
Protection (fuse)
Series Circuit
Voltage Divider.
Voltage is divided proportionally after each resister.
The biggest resistance gets the largest V drop and the smallest R gets the smallest V drop.
Current is constant. It only has one path to flow.
The same current flows through the circuit:
The total V = the total V drop across the individual loads in the circuit:
The voltage-drop in R3, R2, and R1 must equal the voltage rise at Et. Otherwise, something is wrong.
Parallel Circuit
Current Divider.
Voltage is constant across entire circuit.
Just like your house, which is wired in parallel, voltage is constant everywhere.
Voltage rise is distributed equally across all resisters. If you have 120v, you will still have 120v after each R.
The same V is applied to each branch of the circuit.
Current Flow can be varied by
Changing the Voltage. More V = More I. Less V = Less I.
Changing the Resistance. More R = Less I.
Total Current = the sum of the individual branch currents in the circuit:
The reciprocal of the total R = the sum of the reciprocals of the individual branch resistances:
Ohms Law =
Kirchhoff’s Current Law:
The algebraic sum of all the currents entering and leaving a junction = 0
Kirchhoff’s Voltage Law:
The algebraic sum of all the voltages around a closed circuit = 0
The rate at which work is being done.
The rate at which energy is delivered to a circuit.
The rate at which energy (heat) is dissipated by resistance in a circuit.
Work is done when a force causes motion.
Force = Voltage
Current = Motion
Voltage creates current, causing electrons to move in a circuit.
Electric Power Rate – The instantaneous rate at which work is done. What is the pressure and current right now.
Measured in Watts.
Watt is the basic unit of power.
Power is Voltage times Current.
Represents the rate at which work is being done.
Power is always additive whether series or parallel.
In a typical circuit, the power dissipated will usually be less than 1 watt.
milliwatt (mW) =
microwatt (µW) =
Series:
Current is constant.
Voltage divider.
Resistance is additive.
Power is additive.
Parallel:
Voltage is constant.
You will find the same voltage across all components.
To solve for values in a circuit:
Find total resistance.
Determine total current.
Determine the voltage drops and dissipation.
Voltage Dividers
Used to set a bias or operating point of various active electronic components.
Turn on Transistors
Integrated Circuits
Used to divide a higher voltage to a lower voltage.
This process is often referred to as scaling.
Current = Voltage / Resistance.
Current Division
Current is directly proportional to voltage across a circuit.
If voltage increases, current increases.
If voltage decreases, current decreases.
EDrop = ESource * RDrop / RTotal
Loaded Voltage Divider:
Total Load Current is 10.5A. 10A from the Radar load and 0.5A from the radio load. There are only two loads in this circuit.
The bleeder current: The current flowing through the first resister that starts the voltage division process.
The bleeder current needs to be 1/10th of the total load current.
Color Code:
Red – North pole
Blue – South pole
Flux Lines:
North to South
Form complete loop
Don’t cross each other
Tend to form the smallest possible loop.
Permeability – The ability of a material to accept magnetic lines of force. e.g., A Fridge.
Electromagnets:
Composed of many turns of wire close together.
Flux lines are brought together.
The flux lines are then concentrated in the center of the loop.
North and South poles are established.
Increase the strength 3 ways:
More turns of wire.
Increase current.
Insert a ferromagnetic core into the center, usually iron.
Magnetic Induction – The effect a magnet has on an object wo physical contact.
Retentivity – The ability of a material to retain its magnetic field after the magnetizing force is removed.
Magnetic Shields – Low reluctance materials used to protect electronic equipment from magnetic flux lines.
Electromagnetic Induction – The principle behind the generation of electricity.
A current is produced when a conductor passes or is passed by a magnetic field.
As the conductor passes through the magnetic field, a deficiency of electrons is created.
This results in a difference of potential between the end of the conductor.
When the conductor is removed from the magnetic field, the free electrons return to their parent atoms – we call this current.
Faraday’s Law – The induced voltage in a conductor is directly proportional to the rate at which the conductor cuts the magnetic lines of force.
This is the most popular way of producing electricity.
Relay
An electromagnetic switch that opens and closes with an electromagnetic coil.
Used where one circuit needs to control another circuit.
Electrically isolates two circuits.
Also used to control several circuits a distance away e.g., doorbell.
Solenoid
A coil, when energized, pulls a plunger that does some mechanical work.
Door Chimes.
Automotive starters.
Loud Speaker – Constructed of a moving coil around a permanent magnet.
Inductance
The characteristic of an electrical conductor that opposes a change in current flow.
Symbol: L
Measured by the Henry, Symbol: H.
Inductor
Something that has the property of inductance.
A device that stores energy in a magnetic field.
Once a current is moving through a conductor, inductance helps to keep it moving.
As the magnetic flux lines build up, they create an opposition to the flow of current.
Lenz’s Law – An induced emf in any circuit is always in a direction to oppose the effect that produced it. The amount of counter emf is in proportion to the rate of change. The faster the rate of change, the greater the counter emf.
Inductors
Designed to have a specific inductance.
Consists of a conductor coiled around a core.
Classified by the type of core material, magnetic or nonmagnetic.
Types of Inductors
Air Core – Used for up to 5mH of inductance.
Iron Core – Used up to 200mH of inductance.
Toroid Core
Donut shaped.
Offers high inductance for small size.
Magnetic field is contained in the core.
Very prolific.
Inductors can be connected in series or parallel.
Series – treat them as resistors, you add up the total H.
Parallel – treat them as resistors in parallel, see formula.
An inductor is a specific device designed to pocess the property of inductance. Inductance is that property that tries to oppose a change in current.
When a switch is flipped on – putting the circuit into growth mode, current will flow until it hits the inductor. The inductor will fight the current, but eventually lose. The current will then be at 100%. Then the curly wire will have no effect on the electrons. Then we turn the switch off – we put it in decay mode. The magnetic field that was built up around the unductor will collapse into itself. This will induce current—a counter current going back the other way. This current will flow until it dissapates.
Time constants
The time required for current through a conductor to increase 63.2% or decrease to 36.8% of the maximum current. After 5 time constants, we say it’s 100%. Multiply by 5 to get to 100%.
It takes 5 time constants to fully build up or collapse the magnetic field of an inductor.
LR is the sumbol used for the time constant of an RL circuit.
t = seconds.
L = Inductance measured in H.
R = Resistance in Ohms.
t = L/R
Capacitance
The ability of a device to store electrical energy in an electrostatic field. Inductors were electromagnetic.
A large amount of current in a short amount of time – opposite of a battery.
Basic usit is the Farad, symbol: F
A Farad is the amount of capacitance that can store one coulomb (C) of charge when the capacitor is charged to 1 volt.
Usually use microfarads.
Factors affecting capacitance.
Area of the plate. – The bigger the plate, the more electrons you can park on it. Affects Q.
Distance between plates. – The further the plates are apart, the more storage you can have. Affects V. Higher V lowers C.
Type of dielectric material. – Will affect V.
Temperature.
C = Q/V
Capacitor
Symbol: C
A device that possesses a specific amount of capacitance.
Made of two conductors separated by an insulater.
The conductors are called plates.
The insulators are called dielectrics.
Treat all capicitors as if they were charged.
Can hold a charge indefinitely if it doesn’t have a discharge path.
Dialectric Constant
A measure of the effectiveness of a material as an insulator.
Wax Paper: Between 2 and 3. Used before WW2.
Mica: Between 5 and 6.
Tantilum: Between 90 and 170.
Electrolytic Capacitors
Large capacitance for size and weight.
Polarized. They have a + and – lead.
If you put one in backwards, it will explode.
Ceramic Disk Capacitors
Cheap to produce.
Used for 0.1µF or smaller.
Ceramic is the dielectric.
Relaible general purpose
Not electrolytic, they don’t have a +/- lead.
Variable Capacitors
Padders
Trimmers
Tuners
RC Time Constants
When the switch closes, the C will be at 0V and will start charging up to 100%. How long will it take to get to 100%? 5-time constants. 1 time constant = RC. When C is at 100% after the passage of 5-time constants, what V will be across R1? 0. As the capacitor is increasing in voltage, the resistor is decreasing in voltage. This is also a voltage divider. After 5-time constants, the voltage at the cap will be equal to what is at the battery which leaves 0 at the resistor – Kirchhoff’s voltage law.
AC Generator
Produces an alternating voltage using the principles of electromagnetic induction.
Cycle – each time the generator completes one revolution.
Its output voltage is referred to as one cycle of output voltage.
Produces one cycle of output current in a complete circuit.
The 2-halves of the cycle are called alternations.
Cycles
One cycle per second is called a Hertz (Hz).
Sin (180) = 0%
Sin (90) = 100%
AC Values
Each point on the sine wave has 2 values.
The ° of rotation – the ° to which the armature has turned.
The amplitude – the maximum departure of the value an alternating current or wave from the average value.
Peak Value – the absolute value of the point on the waveform with the greatest amplitude.
Effective Value
The amount that produces the same ° of heat in a given resistance as an equal amount of direct current.
Can be determined by the root-mean-square process.
Also called the rms value.
It will have the same effect as if you were applying DC.
ERMS = 0.707P
Period
The time required to complete one cycle of a sine wave.
Measured in seconds.
The letter t is used to measure period.
Frequency
The number of periods that occur in a specific period of time.
Expressed as cycles per second.
A Unit of frequency is called hertz.
One hertz equals one cycle per second. Hz == Cycles per second.
Period t = 1/frequency.
Wall outlet is 60hz. So,
So, the sine wave out of the wall repeats itself every 16.6ms.
AC must be converted to DC before it can be measure.
Rectification – the process of converting AC to DC.
Oscilloscopes
Provides a visual of what is occurring.
The frequency of the signal.
The duration/period of the signal.
The shape of the signal.
The amplitude of the signal.
Marked in cm across vertical and horizontal face.
Capacitors in an AC circuit
AC Voltage, applied to a capacitor, gives the appearance that electrons are flowing in the circuit.
Current and voltage do not flow in phase with each other.
Current leads voltage.
90° out of phase.
Voltage is always 90° behind current.
As voltage in the circuit increases, current decreases.
I_E – in a capacitive circuit, Current leads Voltage by 90°.
Capacitive Reactance.
The opposition that the capacitor offers to the applied AC voltage.
Abbreviated: XC
Measured in Ohms
Impossible to track time constants, so they came up with this.
f = frequency measured in Hertz; c = capacitance measured in Farads.
Now you have the Capacitive Reactance measured in ohms.
Applications
Can be combined with resistors to form RC networks.
Series RC Circuits
Filters – a circuit that discriminates among frequencies
Low-pass filter
High-pass filter
Difference between low/high pass filter is: where I connect the output.
Speaker subwoofer/tweeter/Cross-Over info was here.
Decoupling – AC/DC series RC circuit. Let the AC pass but block the DC.
Coupling – Allows the AC to pass while attenuating or eliminating the DC.
Phase Shift
Attenuate – the opposite of amplify.
Inductance in AC Circuits
Inductors offer opposition to current flow.
Voltage placed across an inductor creates a magnetic field.
When AC voltage changes polarity, it causes the magnetic field to expand and collapse.
Voltage is induced in the inductor coil is called a counter-electromotive force CEMF.
CEMF
Always 180° (did he mean 90?)out of phase with applied voltage.
Opposes the applied voltage.
Opposition is as effective in reducing current flow as a resistor. Using an inductor does not consume power.
Voltage is leading current by 90° (second pic.). Current is lagging.
When voltage is 90, current is 0.
When voltage is 180, current is 90.
When voltage is 270, current is current is 180.
When voltage is 360, current is current is 270.
Inductive Reactance
The opposition offered to current by an inductor.
Measured in Ohms.
Depends on its inductance and the frequency of the applied voltage.
Expressed as XL
f = frequency in hertz
L = inductance in Henries
Applications of Inductive Circuits
Compete with capacitors for filtering and phase shift.
Inductors have fewer applications because they are:
Larger
Heavier
$
Inductors provide a reactive effect while still completing a DC circuit path.
Capacitors provide a reactive effect but block the DC elements.
AC Series RL Circuit:
Vi must have
Voltage
Frequency
Resistor measured in Ohms
Inductor measured in Henries – which must be converted to Ohms with XL formula.
At a low frequency, all of the voltage drop will be on the resistor because at a low frequency, the inductor will look like a piece of wire(curly).
If I take the output across the resistor:
If I take the output across the inductor:
The frequency above or below the frequencies passed (aka attenuated) is called the cut-off frequency.
Symbol: fco (frequency of cut-off)
fco = R / 2πfL
ELI the ICE man
In an inductive circuit, voltage leads current by 90°.
In a capacitive circuit, current leads voltage by 90°.
Not taking notes.
Impedance
The combined effect of resistance and reactance.
Symbol: Z
Materials with more than 3 but fewer than 5 electrons in outer shell.
Silicon
Germanium
Carbon
P and N type materials