Circuit Lab

Digital Logic

2 types of digital logic circuits -- combinational and sequential 0 is false, 1 is true

Circuit

A closed loop conducting path in which an electrical current flows

PN junction I-V characteristics

A p-n junction or junction diode usually allows current through in two main modes Forward Bias (or on) with relatively low resistance, but a forward bias voltage occurs above the Forward Bias voltage (0.3V for Ge and 0.7V for Si) Reverse Bias (or off) with very little current/high impedance below the Forward bias voltage up to the Reverse Breakdown Voltage Below the Reverse Breakdown Voltage the current avalanches through the PN junction and we have a Zener Breakdown or Avalanche current with very high reverse current Some diodes are specifically designed to operate in this region, others will be damaged

Forward Biased P-N Junction

A p-n junction with a voltage at or above the Forward Bias voltage is called forward biased At this point the diode is considered on The area between the n and p regions is called the depletion area In forward bias, the depletion area if very small and current can flow with very little impedance When a diode is connected in a Forward Bias condition, a negative voltage is applied to the N-type material and a positive voltage is applied to the P-type material If this external voltage becomes greater than the value of the potential barrier, approx. 0.7 volts for silicon and 0.3 volts for germanium, the potential barriers opposition will be overcome and current will start to flow. This is because the negative voltage pushes or repels electrons towards the junction giving them the energy to cross over and combine with the holes being pushed in the opposite direction towards the junction by the positive voltage This results in a characteristics curve of zero current flowing up to this voltage point, called the "knee" on the static curves and then a high current flow through the diode with little increase in the external voltage as shown below.

Reverse-biased p-n junction

A p-n junction with a voltage below the forward biased voltage is called reverse biased At this point the diode is considered off The area in between the n and p regions is called the depletion area In reverse bias, the depletion area becomes larger and virtually no current can flow When a diode is connected in a Reverse Bias condition, a positive voltage is applied to the N-type material and a negative voltage is applied to the P-type material. The positive voltage applied to the N-type material attracts electrons towards the positive electrode and away from the junction, while the holes in the P-type end are also attracted away from the junction towards the negative electrode. The net result is that the depletion layer grows wider due to a lack of electrons and holes and presents a high impedance path, almost an insulator The result is that a high potential barrier is created thus preventing current from flowing through the semiconductor material.

Capacitors

A passive two-terminal electrical component that stores potential energy in an electric field For parallel plate capacitors, C = ε₀A/d, ε₀ = 8.854 × 10^-12 C = q/V, q = charge, V = voltage Capacitors are basically devices that store voltage from circuits For capacitors in parallel, Ceq = ∑C For capacitors in series, 1/Ceq = ∑1/C Potential energy of capacitors = ½q∆V = q²/(2C) = ½C(∆V)² Most contain at least two electric conductors often in the form of metallic plates or surface separated by a dielectric medium (glass, ceramic, plastic, paper, mica) A conductor may be a foil, thin film, sintered beads of metal, or an electrolyte Unit of capacitance is a Farad (F). Most capacitors have small values like μF, pF, etc. Charge equals capacitance times potential Q=CV Consists of two conductors separated by a non-conductive region where charge builds up on both sides When charging the current flows freely at first so it appears to be short (with zero voltage) When fully charged the current is completely stopped so it appears to be an open (with max voltage) A capacitance of one Farad (F) means that one Coulomb of charge on each conductor causes a voltage of one Volt across the device (Q=VC) The simplest model consists of two parallel plates with a thin dielectric in between Dielectric is much thinner than the dimensions of the plates Dielectric permittivity of the material determines how much capacitance can be held Free space/vacuum has a permittivity of εo = 8.854 x 10^-12 F/m, all other materials are higher

Loop

A simple closed path in a circuit in which no circuit element or node is encountered more than once

Path

A single line of connecting elements or sources

Mesh

A single open loop that does not have closed parts No components inside one of these

Branch

A single or group of components such as resistors or a source which are connected between two nodes

Magnet shapes

All have a North pole and a South pole 1. Horse shoe magnet 2. Ring magnet 3. Cylindrical magnet 4. Bar magnet 5. Button magnet 6. Square magnet 7. Arc/ Crescent magnet

AC current

Alternating currents Change directions Sinusoidal waves so they vary with time Produced from power supplies and AC generators In the US, 120 volts and 60 hertz cycles per second (change direction 60 times per second) Used to power motors found in refrigerators, trains, computers, hard drives, industrial machinery, household appliances, and many other electronic devices Produce electricity by converting mechanical energy into that of electrical Mechanical energy via steam is used to rotate the loops in the magnetic field, and the generated emf is a sinusoidal wave that varies in time More likely to die by this shock than by DC current shock

Magnetic field of an electromagnet

An electromagnet is just a solenoid The core material's permeability can dramatically increase the strength of the electromagnet or solenoid The number of turns over the length or turn density can dramatically affect the strength of the electromagnet or solenoid

Surface mount and through hole switches

As with most components, the termination style of a switch always comes down to either surface mount (SMD) or through-hole (PTH). Through-hole switches are usually larger in size SMD switches are smaller than their PTH counterparts. They sit flat, on top of a PCB. SMD switches usually require a gentle touch, they're not built to sustain as much switching force as a through-hole switch.

Double throw double pole

Basically two SPDT switches, which can control two separate circuits, but are always switched together by a single actuator. DPDTs should have six terminals

Switches

Can only exist in one of two states: open or closed. In the off state, one of these looks like an open gap in the circuit. This, in effect, looks like an open circuit, preventing current from flowing. In the on state, a this acts just like a piece of perfectly-conducting wire. A short. This closes the circuit, turning the system "on" and allowing current to flow unimpeded through the rest of the system. In order to change from one state to another, one of these must be actuated. That is, some sort of physical action must be performed to "flip" the state. The actuation-method of one of these is one of its more defining characteristics. One of these must have at least two terminals, one for the current to (potentially) go in, another to (potentially) come out. The number of poles* on one of these defines how many separate circuits this can control. So one of these with one pole, can only influence one single circuit. A four-pole version of this can separately control four different circuits. one of these's throw-count defines how many positions each of it's poles can be connected to. For example, if one of these has two throws, each circuit (pole) in this can be connected to one of two terminals.

NC switch

Conversely, if a button usually acts like a short circuit unless actuated, it's called a normally closed switch. These are "push-to-break"; actuating the switch creates an open circuit

NOR gate

output is 1 if BOTH inputs are 0 A NOR B is written as (A + B)' or (A + B)

AND gate

output is 1 if BOTH inputs are 1 A AND B should be written as AB (or sometimes A • B)

XOR gate

output is 1 if ONLY one input is 1 should be written as A ⊕ B

Combinational logic circuits

respond as soon as the input changes

Resistor marking

Electronic color code developed in early 1920s Sometimes the resistance is printer directly on the resistor to avoid confusion, especially for colorblind people first band is the first significant digit of the component second band is the second significant digit third band is the decimal multiplier (what power of ten to multiply by) fourth band (if present) indicates the tolerance- no fourth band means 20% tolerance

Kirchhoff's second law

"in any closed loop network, the total voltage around the loop is equal to the sum of all the voltage drops within the same loop"

Kirchhoff's first law

"total current or charge entering a junction or node is exactly equal to the charge leaving the node as it has no other place to go except to leave, as no charge is lost within the node" I(exiting) + I(entering) = 0 A node is a connection or junction of two or more current-carrying paths or elements such as cables and components, indicated by a dot For current to flow either in or out of a node a closed circuit path must exist This law can be used when analyzing parallel circuits

Kinetic Energy

Measured in Joules (J) Energy of something that is moving ½ m(v^2)

Torque problems with a DC motor

The brushes wear out The angular force or torque changes as the rotor spins around For a single coil system the torque goes to zero at 180 For two coil systems you can greatly increase the average Torque and smooth out the force

Brushed vs non-brushed DC motors

Brushed motors are the most common, but the brushes eventually wear out- especially if the motor was used with too much power, too fast, or it not cleaned The brushes charge the commutator inversely in polarity to the permanent magnet, in turn causing the armature to rotate. The rotation's direction, clockwise and/or counterclockwise, can be reversed easily by reversing the polarity of the brushes, i.e., reversing the leads on the battery. Non-Brushed Motors use the magnets on the Rotor and then pulse the current on the windings on the Stator. The motor will move as fast as the pulses On the pro side, brush motors are generally inexpensive and reliable. They also offer simple two-wire control and require fairly simple control or no control at all in fixed-speed designs. If the brushes are replaceable, these motors also boast a somewhat extended operational life. And because they need few external components or no external components at all, brush motors tend to handle rough environments reliably. For the downside, brush motors require periodic maintenance as brushes must be cleaned and replaced for continued operation, ruling them out for critical medical designs. Also, if high torque is required, brush motors fall a bit flat. As speed increases, brush friction increases and viable torque decreases. Other disadvantages of brush dc motors include inadequate heat dissipation caused by the rotor limitations, high rotor inertia, low speed range due to limitations imposed by the brushes, and electromagnetic interference (EMI) generated by brush arcing. BLDC motors have a number of advantages over their brush brothers. For one, they're more accurate in positioning apps, relying on Hall effect position sensors for commutation. They also require less and sometimes no maintenance due to the lack of brushes. They beat brush motors in the speed/torque tradeoff with their ability to maintain or increase torque at various speeds. Importantly, there's no power loss across brushes, making the components significantly more efficient. Other BLDC pros include high output power, small size, better heat dissipation, higher speed ranges, and low-noise (mechanical and electrical) operation. Nothing is perfect, though. BLDC motors have a higher cost of construction. They also require control strategies that can be both complex and expensive. And, they require a controller that can cost almost as much as if not more than the BLDC motor it governs.

DC Motor

Brushes (normally made out of carbon) allow the current to continue even as the Rotor rotates There is a small gap when the brushes switch from one set of windings to the next (causing the switch of polarities) on the Commutator Commutator is a metal ring that is fixed on the shaft of the motor, so it rotates too

Static electricity

Created by bringing two different materials into contact, causing one material to strip the other of electrons Hazards are that a spark from this could cause an explosion if exposed to flammable gases It is dangerous when you touch something with a large electric charge on it. The charge will flow through your body causing an electric shock. This could cause burns or even stop your heart

Conventional Flow

Current goes from + to - What we pretend happens

Electron Flow

Current goes from - to + What actually happens

Magnetic field of a solenoid

Current going through a multiple wire loops causes a magnetic field similar to a bar magnet The magnetic field is concentrated inside the loops Have your right hand fingers follow the current The magnetic flux (B) goes through the loop with your right thumb

Magnetic field of current

Current going through a wire causes a magnetic field going around it in a "right hand rule" Point your right thumb in the direction of the current The magnetic field (B) goes around the wire like your right hand fingers

Magnetic field of current loop

Current going through a wire loop causes a magnetic field that is concentrated in the inside of the loop Have your right hand fingers follow the current The magnetic flux (B) goes through the loop with your right thumb

How a motor works

DC motor has two windings and two permanent magnets Coils are powered from the Commutator and the Brushes The current that runs through each windings changes direction at the halfways point (caused by the connection of the commutator) Magnets are wound such that when one is North, the other is South In the simple motor shown above the current in the rotating coil is reversed every half-turn by an automatic switching arrangement consisting of a split metal ring called a commutator. The rotating part of the motor is called the armature and consists of a coil with many turns of wire. The armature is mounted on an axis between two fixed magnetic poles. Each end of the armature is attached to one end of the commutator (see red arrows). Current enters the commutator via one brush connected to a battery. Current leaves the armature via the second brush which is in contact with the other half of the commutator. Since the brushes are fixed when the commutator rotate , each brush is in contact with one half of the commutator during one half-turn and with the opposite half or the commutator during the second half-turn. As a result, the current in the armature reverses its direction every half turn and provides the conditions necessary to keep the armature rotating

Operational Amplifiers

DC-coupled high-gain electronic voltage amplifier with a differential input and, usually, a single-ended output Popular due to versatility as a differential amplifier Can be used as a comparator, inverting amplifier, or non-inverting amplifier NEVER use a KCL at the output of an Op-Amp Ideal Op-Amps Infinite Open-Loop Gain (G) Infinite Input Impedance (Rin) Infinite Out Voltage Range (vout max) Infinite Common-Mode Rejection Ratio Infinite Power Supply Reject Ratio Zero Input Offset Voltage Zero Output Impedance (Rout) Zero Noise Zero Input Current (vin/Rin) None of these are actual Two golden rules for ideal Op-Amps V+=V- Current is zero at V+ and V- Operational amplifiers are linear devices that have all the properties required for nearly ideal DC amplification and are therefore used extensively in signal conditioning, filtering or to perform mathematical operations such as add, subtract, integration and differentiation. An Operational Amplifier, or op-amp for short, is fundamentally a voltage amplifying device designed to be used with external feedback components such as resistors and capacitors between its output and input terminals. These feedback components determine the resulting function or "operation" of the amplifier and by virtue of the different feedback configurations whether resistive, capacitive or both, the amplifier can perform a variety of different operations, giving rise to its name of "Operational Amplifier". An Operational Amplifier is basically a three-terminal device which consists of two high impedance inputs. One of the inputs is called the Inverting Input, marked with a negative or "minus" sign, ( - ). The other input is called the Non-inverting Input, marked with a positive or "plus" sign ( + ). A third terminal represents the operational amplifiers output port which can both sink and source either a voltage or a current. In a linear operational amplifier, the output signal is the amplification factor, known as the amplifier's gain ( A ) multiplied by the value of the input signal and depending on the nature of these input and output signals, there can be four different classifications of operational amplifier gain​.

DC currents

Direct currents Only flow in one direction Are constant in time Produced from power supplies, batteries, and DC generators Similar to their AC counterparts, but they have a generated EMF that is direct current Found in power tools, portable radios and televisions, toys, and many other devices Diagrams are the usual diagrams from physics Causes less damage than AC current

Georg Ohm

Discovered Ohm's Law R = V/I R is resistance (Ω), I is current (A), V is the change in voltage (V)

Michael Faraday

Discovered electromagnetic rotation, which eventually developed into the electric motor Proved that gases could be liquified at low temperatures/high pressures Discovered Benzene Discovered that a varying electric field causes electricity to flow in an electric circuit Discovered that when any electric conductor becomes charged, all extra charge sits on the surface of the conductor Discovered that a magnetic field causes the plane of light polarization to rotate Discovered that all substances are diamagnetic, meaning that they oppose the direction of applied magnetic fields Created laws of electrolysis Electrolysis is an electrochemical process by which current passes from one electrode to another in an ionized solution that is an electrolyte; In this process, positive ions or cations come to the negative electrode or cathode and negative ions or anions come to the positive electrode or anode the chemical deposition due to flow of current through an electrolyte is directly proportional to the quantity of electricity (coulombs) passed through it when the same quantity of electricity is passed through several electrolytes, the mass of the substances deposited are proportional to their respective chemical equivalent or equivalent weight Chemical equivalent = atomic weight/valency

Heinrich Hertz

Discovered radio waves Discovered the photoelectric effect, which is the phenomenon that shining ultraviolet light on electrically charged metal caused it to lose charge faster than it would otherwise

Electric fields

Field lines are perpendicular to the surface charge Field lines never intersect each other kq1/d^2, k = 8.99 x 10^9 Field is strong when field lines are close together Number of field lines is proportional to magnitude of charge lines of these start at positive charge and end at negative charge If the charge is single, the field starts or ends at infinity

Lorentz force law

Force is applied on all charged particles by both magnetic and electric fields The Force of the Electric field is equal to F elect=qE and is in the direction of the Electric field The force of the magnetic field is equal to Fmag=qvBsinΦ and is in the direction diagonal to the magnetic field and the moving charge If the charge isn't moving there is no magnetic force If the charge is moving in the line of the magnetic field there is no magnetic force

Transient charging of RC circuits

If starting an RC circuit discharged, Vc(t=0) = 0V If switch is turned to a charging position at t=0, the capacitor begins to charge The charge as a function of time increases Q(t) =Vmax (1-e^t/RC) V(t) = Vmax(1-e^t/RC) I(t) = (Vmax/R)e^t/RC

Transient discharging of RC circuits

If starting discharged, Vc(t=0) = Vb If switch is turned to a (discharging position) at t=0, the capacitor begins to discharge, from Vmax τ = RC Vmax = Vb (since eventually the current through R goes to zero and so the voltage at Vb = Vc The charge as a function of time decreases Q(t) =(Vmax /C)(e-t/RC) V(t) = Vmax(e-t/RC) I(t) = (Vmax/R)e-t/RC

North and South Poles

If you break a magnet in half, it forms two magnets- each with a North and South pole The magnetic field can be displayed by lines drawn from the North pole to the South pole

Power Factor

In a normal AC waveform graph, there is both a voltage vs. time waveform and a current vs. time one. The two are normally in sync and always have positive power (signs switch as the zero-crossing, so the product is always positive). This occurs in a purely resistive load like a perfect lightbulb, and when the two are in sync, this is always 1, a perfect version of this. However, this never happens. On the other hand, when the voltage and current are 90 degrees out of phase, the power transfer is half negative and half positive, so there is no net power transfer. This occurs in a purely inductive or capacitive load (i.e. a motor), and this is 0. This also never happens. In the real world, every wire has resistance, inductance, and capacitance (they are very negligible, small wire is in the 1-10 milliohms/ft), which causes this to never be perfect. Although there are many units that go along with AC, the most important are: watts, which are real power, the work that can be done through a motor; volt-amps (VA) are apparent power, the power that wires and cables must handle; volt-amps-reactive (VAR) are the power the wires must carry, but cannot do real work. These three main units are related in the power triangle shown to the right. Most power companies do not want reactive power, charging more for businesses with low loads of these (bigger wires are needed), and inductors or capacitors can be placed to correct for the bad this. However, there are some uses for reactive power. For example, in drilling rigs, when a rig holds the top drive, most rigs using AC motors don't actually use any power. They only use enough to overcome the resistive losses in the wire/control system (VFD) and motor, approximately 50A at 60V, or 30KVA. This is a tiny amount of power to hold a block weighing a little over a million pounds. This occurs because about 1200A (720KVA) flows between the motor and the VFD, but the motor is almost a purely inductive load, so no real power is used.

Alessandro Volta

Invented the first electric battery (voltaic pile, used copper and zinc) Using his invention, scientists were able to produce steady flows of electric current for the first time First person to isolate methane Discovered that methane mixed with air could be exploded using an electric spark, which is the basis of the internal combustion engine Discovered contact electricity that results from contact between different metals Recognized two types of electric conduction Wrote the first electromotive series that showed the voltages that different metals can produce in a battery from lowest to highest Discovered that electric potential in a battery is directly proportional to electric charge Improved and popularized electrophorus Proved that electricity could be generated chemically

Single pole single throw

It's got one output and one input. The switch will either be closed or completely disconnected. SPSTs are perfect for on-off switching. They're also a very common form of momentary switches. SPST switches should only require two terminals.

Potential energy

Measured in Joules Something's potential for energy

Resistance

Measured in ohms (Ω) Equivalent of this in series circuits is the sum of all resistors For parallel circuits 1/Equivalent of this = 1/r1 + 1/r2 + 1/r3 + ... this property of material = ρL/A, ρ = resistivity of material Many resistors and conductors have a uniform cross-section with a uniform flow of electric current and are made of one material This increases: Longer lengths, Less area/ smaller cross-section, Higher temperature, Less conductive material This decreases: Shorter lengths, Larger area/ cross-section, Lower temperature, More conductive material

Power

Measured in watts (W) Rate of electrical transfer P = iV = i²R = V²/R

Gravitational potential energy

Mgh, m = mass, g = gravity acceleration, h = height

RC circuit

Most RC problems involve a Resistor (R) and a Capacitor (C), which is charged by a battery and then discharged for the start Usually with a switch that is set to charge or discharge the capacitor The time constant, τ = RC, is in unit of seconds τ is the time it takes to charge a capacitor to about 63% of max value τ is the time it takes to discharge a capacitor to about 37% of its original value Charge and voltage don't change instantaneously so they are the same right before and right after the switch Current starts as a short when charging and goes to zero long term. Current starts at maximum value (i.e. if it was a short during charging) when discharging and goes to zero long term

Electric Motors

Motors that turn flowing electric current into mechanical motion/ work They are the opposite of generators, which turn mechanical motion/ work into following electrical power To make one you need a magnetic field and a flowing current. Like with an electromagnet, the more turns, the more powerful the magnetic field

Right hand rule

Palm of right hand on velocity vector, curl fingers towards magnetic field vector, wherever your thumb points is the direction of magnetic force

Time constant of an RC circuit

Resistance * capacitance

Single pole double throw

SPDTs have three terminals: one common pin and two pins which vie for connection to the common. SPDTs are great for selecting between two power sources, swapping inputs, or whatever it is you do with two circuits trying to go one place. Most simple slide switches are of the SPDT variety. SPDT switches should usually have three terminals

Semiconductor doping

Semiconductors can be doped with different materials to provide excess holes (positive charges) or electrons (negative charges)

Multiple sources

Sometimes a circuit has more than one source Voltage sources should be added in series Current sources should be added in parallel You should NOT put voltage sources in parallel or current sources in series, as it can create a situation that violates circuit rules

Thevenin Equivalent

The circuit of this type between two points consists of a voltage source in series with a resistor. In order to find the Thevenin voltage, you must find the open-circuit voltage across the two points (ie when it is broken open). The resistance is found by removing all the power sources (replacing current sources with shorts and voltage sources with breaks) and finding the equivalent resistance of the resultant resistor network.

Norton Equivalent

The network can also be represented by this. It consists of a resistor in parallel with a current source. The Norton resistance is equal to the Thevenin resistance. The current of this is equal to the current that passes between the two points if you short circuit them.

Parts of the motor

The part that rotates in the middle is called the rotor In a Brushed DC motor, this has the windings Armature is the part that contains the main current-carrying winding. The armature usually consists of a coil of copper wire wound around an iron or steel core The part that doesn't move on the outside is called the Stator Every electric motor has two essential parts: one stationary, and one that rotates. The stationary part is the stator. Though configurations vary, the stator is most often a permanent magnet or row of magnets lining the edge of the motor casing, which is usually a round plastic drum. An electric motor has another important component, the commutator, which sits at one end of the coil. It is a metal ring divided into two halves. It reverses the electrical current in the coil each time the coil rotates half a turn. The commutator periodically reverses the current between the rotor and the external circuit, or the battery. This ensures that the ends of coils do not move in opposite directions, and ensures that the axle spins in one direction. The commutator is necessary because the spinning rotor gets its motion from magnetic attraction and repulsion between the rotor and the stator. To understand this, imagine the motor turning in slow motion. When the rotor rotates to the point where the south pole of the rotor magnet meets the north pole of the stator, the attraction between the two poles will halt the spin in its tracks. To keep the rotor spinning, the commutator reverses the magnet's polarity, so the rotor's south pole becomes the north. The north pole of the rotor and the north pole of the stator then repel each other, forcing the rotor to continue to spin. At one end of the motor are the brushes and the terminals. They are at the opposite end from where the rotor exits the motor casing. The brushes send electrical current to the commutator and are typically made of graphite. The terminals are the locations where the battery attaches to the motor and sends the current to spin the rotor.

Short circuit

This is simply a low resistance connection between the two conductors supplying electrical power to any circuit. This results in excessive current flow in the power source through the 'short,' and may even cause the power source to be destroyed. If a fuse is in the supply circuit, it will do its job and blow out, opening the circuit and stopping the current flow. One of these may be in a direct- or alternating-current (DC or AC) circuit. If it is a battery that is shorted, the battery will be discharged very quickly and will heat up due to the high current flow. Can produce very high temperatures due to the high power dissipation in the circuit. If a charged, high-voltage capacitor is short-circuited by a thin wire, the resulting huge current and power dissipation will cause the wire to actually explode.

Tolerance

This is the percentage of error in the resistor's resistance, or how much more or less you can expect a resistor's actual measured resistance to be from its stated resistance This quality of fourth band of resistor is this for the whole resistor, if no fourth band, then this is 20%

Light Emitting Diode (LED)

Two-lead semiconductor light source p-n junction diode that emits light when activated Color is determined by the energy band gap of the semiconductor, which also affects the voltage drop

Nikola Tesla

Used alternating current to transport electricity in a grid, which was much more efficient than direct current Helped with the development of turbines and generators Invented AC induction motor Invented wirelessly controlled boat

NO switch

When a button is open until actuated, it's said to be normally open. When you actuate one of these, you're closing the circuit, which is why these are also called "push-to-make" switches.

Magnetic attraction and repulsion

When magnets are near, the lines of force go from North to South pole from the two magnets North pole would be attracted to the South pole North pole would be repulsed from the North pole

Current

When you are showing the direction of this on a diagram, you show the direction that protons would flow, despite the fact that protons can't flow and it is the electrons that are flowing I = V/R, dq/dt Units are amperes (A)

Polyphase

Whereas a single phase system has one wire with changing voltage, this type of system has multiple wires carrying current at a time, shifted (time delayed) by a certain amount. The most common is 3-phase power, which is used in many factories and industrial places, anywhere where large motors are involved. In this system, there are 3 wires carrying power, each of them shifted 120 degrees from the other. In this case, there is always a voltage between the phases (due to the shift) and a neutral is not required. The benefit to this is that the power through the system is constant, instead of varying like single phase (add up the magnitude of the 3 waves at any point and it will always be the same number). This type of system is also useful in motors because the motors become self-starting; in an AC motor, the magnetic field must come from two points, and there must be a phase shift between the two so that the field 'rotates' around the stator (motor shaft). In a single phase system, this isn't possible, so most motors need to be moving to start (so the stator is already moving through the field), in three phase, the phase shift is already present, so the motor can start itself, it can also apply full torque without any speed, because the field can 'hold' the stator in place. This is useful in cranes and oil derricks, removing the need for a mechanical break. Systems that use more than 3 phases exist, but almost solely for motor applications where higher speeds are required

Reverse Breakdown of Biased Junction

Zener diode or "breakdown diode" are basically the same as the standard PN junction diode but are designed to have a low and specified Reverse Breakdown Voltage which takes advantage of any reverse voltage applied to it You use these to enter the breakdown or zener region to get very low impedance (all voltage below -Vz or Zener Breakdown Voltage)

Ideal diode

Zero resistance in forward bias with the forward bias voltage Infinite resistance in reverse bias Bias voltage for Si ~0.7V

Magnetic compass

a navigational instrument that measures directions using a free-floating magnet and the Earth's magnetic field to point towards the Magnetic North Pole Magnetic North Pole is not quite at the geographical North Pole and it moves Magnetic North Pole is actually a South Pole of Earth's magnetic field- allowing the North pole of this to be attracted these become useless near the poles Invented first by the Chinese during the Han Dynasty. Europe invented the dry version of it around 1300

Current source

a theoretical component which outputs a precise, constant current, regardless of the voltage.

Voltage source

a theoretical component which outputs a precise, constant voltage regardless of current. Their primary usage is in modeling real components. For example, a battery can be modeled as one of these in series with a resistor equal to its internal resistance.

Inverter / NOT gate

aren't truly gates, as they do not make any decisions. The output of one of these is a 1 if the input is a 0, and vice versa NOT A should be written as A'

Multimeter

can measure voltage, current, and resistance. Set this to the mode corresponding to the unit of measurement. Then, place the meter in series if measuring current, or in parallel if measuring voltage

Sequential circuits

have a clock signal, and changes propagate through stages of the circuit on edges of the clock

Toggle Switches

have a long lever, which moves in a rocking motion

Voltage

kq1/d Units are volts (V) Electric potential, potential energy per coulomb, emf Change in this is constant across branches of parallel circuits Change in this across an entire circuit is the same as this from the battery

Coulomb's Law

kq1q2/(d^2) = electromagnetic force Opposites attract, like charges repel Determines the force of attraction or repulsion between the two charges F is the force in Newtons K is Coulomb's constant 8.99 x 10^9 Nm^2/C^2 q1 and q2 are the charges in Coulombs d is the distance in Meters between the centers of charges Groups of charges can be combined into an equivalent charge (like for an ion)

Electric potential energy

kq1q2/d -Ed qΔV

Maintained switches

like the light switches on your wall - stay in one state until actuated into a new one, and then remain in that state until acted upon once again. These switches might also be called toggle or ON/OFF switches. retains its state until it's actuated into a new one

Ammeter

measures the current in a circuit. To use one of these, place the meter in 'series' with the circuit. They have very low resistance, so it has minimal impact to the circuit when placed in series.

Ohmmeter

measures the resistance of a circuit element. It can be placed either in series or parallel to the element. If one of these is not provided, one can also place a Voltmeter parallel to the element and an Ammeter in series with the element and apply Ohm's Law to calculate the resistance.

Voltmeter

measures the voltage between two points in a circuit. To use one, place the meter 'parallel' to the circuit element. It has very high resistance, around 10MΩ, so it has minimal impact to the circuit when placed in parallel.

Momentary switches

only remain active as long as they're actuated. If they're not being actuated, they remain in their "off" state. Ex: keyboard keys When one of these is not actuated, it's in a "normal" state. Depending on how the button is constructed, its normal state can be either an open circuit or a short circuit. switches which only remain in their on state as long as they're being actuated (pressed, held, magnetized, etc.)

NAND gate

output is 1 if AT LEAST one input is 0 A NAND B is written as (AB)' , (A • B)' , or (AB)

OR gate

output is 1 if AT LEAST one input is 1 A OR B should be written as A + B

Load

the amount of power supplied by a source; the resistance of moving parts to be overcome by a motor.

Conductance

the degree to which an object conducts electricity, calculated as the ratio of the current that flows to the potential difference present. This is the reciprocal of the resistance and is measured in Siemens or mhos

Doping

the intentional introduction of impurities into an intrinsic semiconductor for the purpose of modulating its electrical, optical and structural properties. Single semiconductors come from Group 14 of the Periodic Table (Si, Ge, C) P-Type of this usually comes from Group 13—one less electron N-Type of this usually comes from Group 15—one extra electron GaAs is a semiconductor as well (notice how they cancel out)

Transformers

these are basically 2 electromagnets that are put together, most of the time sharing a common core of iron. These work because the AC generates a constantly changing magnetic field in the primary coil, which can induce a charge in the secondary coil. It isn't possible to build a DC transformer because the magnetic field would be constant: remember that stable magnetic fields (stationary) can't induce a charge (a changing field acts the same as a moving one). The ratio of the turns of the primary winding to the turns of the secondary is equal to the ratio of the primary voltage to the secondary (i.e. 2 turns on the primary and 1 on the secondary will halve the primary voltage)

Single Phase AC Current

this (only one wire that's 'hot' or has voltage in it) is most of what's in your home. It has a hot and neutral line. The hotline varies between the minimum and maximum voltage, and neutral stays around 0v. The switch direction does not matter much for simple devices like light bulbs, but more complicated devices generally convert AC into DC before use through a rectifier (usually a diode bridge). As a side note, an inverter is used to convert DC into AC. The benefit of this is that AC enables the use of transformers to easily step-up and step-down the voltage.

Inductor

this is essentially an electromagnet that exhibits special characteristics in a circuit. It can be described as the opposite of a capacitor, but this is slightly misleading. One of these can store a charge in a magnetic field (capacitors store it in an electric field) and can maintain a constant current in a circuit (capacitors maintain a constant voltage). It easily conducts DC (capacitors easily conduct AC), but it AC is put through an inductor, the magnetic field grows and collapses with the rise and fall of the current, which tends to opposes the flow of AC through one of these.

Earth's magnetic field

this is similar to the magnetic field of a bar magnet tilted 11 degrees from the spin axis of the Earth Magnetic fields surround electric currents, so e surmise that circulating electric currents in the Earth's molten metallic core are the origin of the magnetic field Rock specimens of different age in similar locations have different directions of permanent magnetization. Evidence for 171 magnetic field reversals during the past 71 million years has been reported Interaction of the terrestrial magnetic field with particles from the solar wind sets up the conditions for the aurora phenomena near the poles

Diode

two-terminal electronic component that conducts current primarily in one direction Has low resistance (ideally zero) in one direction and high (ideally infinite) resistance in the other Can be replaced with a short (0 ohm) when forward biased or closed switch An open (infinite ohms) when reverse biased or open switch When forward biased has a small resistance and a bias depending upon semiconductor material 0.6-0.7 V for Si diodes 0.25-0.3 V for Ge diodes LEDS can be as high as 4.0V

Wheatstone Bridge

used to measure an unknown resistance value to a high degree of accuracy. It uses 4 resistors set up in a diamond fashion (shown below) and a voltmeter. In the schematic below, Rx is the unknown resistance, R1 and R3 are fixed resistance values (generally the same, but they don't have to be the same, also generally >1% tolerance, but again, not always) and R2 is a variable resistor (potentiometer, this is not always the case, see below). By adjusting R2 until the voltmeter reads 0 volts, you know that the ratio between the R1/R2 and R3/Rx is equal.

DIP switches

​through-hole switches designed in the same mold as a through-hole DIP IC. They can be placed in a breadboard, in the same manner, a through-hole IC might, by straddling the center area. These switches often come in arrays of eight or more separate SPST switches, with tiny little sliding levers. They were widely used in the olden days of computing, but they're still useful for configuring a device via hardware.

Electric charge

∑q = q1 + q2 + q3 + ... Charge is conserved q = ne, where e is the charge of an electron, n is an integer, and q is the total charge t₁∫t₂ i dt The physical property of matter that causes it to experience a force when placed in an electromagnetic field Two types of electric charges; positive and negative: like charges repel and unlike attract; an object with Charge is in unit Coulombs C, always conserved Electron has a charge of 1.602*10-19 C