Equations for Electricity, Electronics, and Electromagnetics
For the sake of sanity, the use of calculus is kept to a strict minimum.

Ohm's Law

  V=IR


    This is the most fundamental of the electrical-related equations.  V stands for VOLTS. I is for current in AMPS.  R is for resistance in OHMS.
 
 

Coulomb's Law

  F=8.9875x109((Q1Q2)/R2)


    This is the most fundamental of the electrical-field related equations.  F is the force in Newtons.  Q1 and Q2 are the individual charge particles (charges in units of coulombs). R is the radius between the two charges in meters.  If one and only one of the charges is negative, then the force will be negative, meaning that the charges are being pulled toward eachother.  Please note that one electron or proton has a charge of 1.6021917 x 10-19 coulombs (electrons having a negative value).
 

Simple Electrical Field

  E=8.9875x109((Q)/R2


    This is a simple electrical-field related equation when one charge ispresent.  E is the electric field in Newtons per coulomb. Q1 and Q2 are the individual charge particles (charges in units of coulombs).  R is the radius between the two charges in meters.  If one and only oneof the charges is negative, then the force will be negative, meaning that the charges are being pulled toward each other.  Please note that oneelectron or proton has a charge of 1.6021917 x 10-19 coulombs (electrons having a negative value).
 

Gauss's Law

F=E*A*COS(q)

    Here is a fundamental equation describing Gauss's Law.  F is the "electric flux."  E is electric field strength in Newtons per coulomb.  A is the area in square meters.  is the angle in which an field field penetrates.
 
 

Resistors in Series

RTotal=R1+R2+R3+...+RN


    Here is a simple equation that adds up all the resistor values in a series configuration to give you a total resistance in RTotal.
 
 

Resistors in Parallel

RTotal=1/(1/R1+1/R2+1/R3+...+1/RN)


    Here is a simple equation that adds up all the resistor values in a parallel configuration to give you a total resistance in RTotal.
 
 

Capacitors in Series

CTotal=1/(1/C1+1/C2+1/C3+...+1/CN)


    Here is a simple equation that adds up all the capacitance values in a series configuration to give you a total capacitance in CTotal.
 
 

Capacitors in Parallel

CTotal=C1+C2+C3+...+CN


    Here is a simple equation that adds up all the capacitance values in a parallel configuration to give you a total capacitance in CTotal.
 
 

Batteries in Series

VTotal=VBattery1+VBattery2+VBattery3+...+VBatteryN


    Using this simple equation, you can get the total voltage of all the batteries connected in a series through VTotal.  However, the maximum overall current will be equal or SLIGHTLY higher than that of the battery with the LOWEST available current.
 

Batteries in Parallel

ITotal=IBattery1+IBattery2+IBattery3+...+IBatteryN


    Using this simple equation, you can get the total current of all the batteries connected in parallel through ITotal.  However, the maximum overall voltage will be equal or SLIGHTLY higher than that of the battery with the LOWEST voltage.
 
 

Simple Capacitance Formula

C=Q/V


    Using this simple equation, you can calculate a capacitor's value.  C is the capacitance in farads.  Q is the charge in coulombs.  V is the voltage.  Please note that the "wallop" from a capacitor is directly proportional to the voltage within it.  BE CAREFUL when getting into those TV's, monitors, oscilloscopes, and the like.  If you touch the wrong parts, the results can be a minimum of being thrown across a room, and the maximum could be a swift and painful death!  Use care when handling capacitors rated 500 mF or greater and/or if the voltage is greater than about 30 volts.  While capacitors at these values won't kill you, you can still get fried, but not well done.  For capacitors at these values or smaller, you can discharge them quickly by shorting their ends together.  For bigger capacitors, you should use a high-power resistor between the terminals, lest you want some 4th of July in your shop!  Even the capacitors used for powering an electronic flash on today's cameras can spark significantly AND carry a whopping 300 volts or more, as well as do a professional job of scaring the daylights out of you if you happen to short this sucker directly.
 
 

The Simple Capacitor

C=(8.8542 x 10-12 K A)/D


    If a person were to make a homemade parallel-plate capacitor, he or she can use this equation. C is the capacitance in farads.  K is the dielectric constant for the material (including air if nothing else is used) between the plates. A is the area of each plate (in square meters). D is the distance between the plates in meters.  Air has a dielectric constant of 1.  At least most other substances have significantly higher dielectric constants, most of which range from around 3-6.
 
 

Amps / Coulomb Relationship

I=C/S


    This equation simply shows the relationship between current and the speed of electrons.  I is the current in amps.  C is the number of coulombs. S is the number of seconds.
 
 

Power

P=VI*COS(q)


    Using this simple equation, you can calculate the power consumed by a device.  Unless you are working with AC power at an angle other than 0 degrees, you can chop off the cosine portion of this equation and make life simple.  P is the power in watts.  V is the voltage supplied.  I is the current (in amps) drawn by the device.
 
 

Power Through a Resistor

P=I2R

Or

P=V2/R


    Using this simple equation, you can calculate the power consumed by a resistor.  P is the power in watts.  R is the resistance in ohms.  I is the current (in amps) drawn by the device.  When using the second equation, V is the voltage across the resistor.
 
 

Resistance of Wire

R=(rL)/A

    This equation kind of shows the quality of wire, particularly when lots of current most travel long distances.  R is the resistance in ohms.  r is the "resistivity" in ohm-meters.  L is the length of the wire in meters.  A is the cross-sectional area of the wire in square meters.  This equation partially shows why bigger wire is needed for devices that use more power.
 
 

Force Between Two Parallel Wires

F/L = (1.257 x 10-6 I1I2)/2pD

    This equation gives the force between two parallel wires, both of which are carrying a current.F is the force in Newtons.  L is the lengthof the wires in meters.  Omit L if you want the TOTAL force. I1 and I2 are the currents in amps. D is the distance between the wires in meters.

Magnetic Force from Wire Carrying a Current

B=(1.257 x 10-6 I)/(2pR)


    This equation gives the magnetic force induced by a wire carrying a current.  is the current in amps.  R is the radius from the CENTER of the wire in meters.  B is the magnetic field in units of tesla.
 
 

Magnetic Force from Object Wrapped with
Wire Carrying a Current (Wire Having Insulation)

B=(1.257 x 10-6 I N)/L

    This equation gives the magnetic force induced by a wire carrying a current.  I is the current in amps.  R is the radius from the CENTER of the wire in meters. B is the magnetic field in units of tesla.  N is the number of turns.  L is a unit length in meters.  To get the entire magnetic field, just omit the division by L and make life simple.
 
 

Magnetic Flux

FB=B*A*COS(q)

    Here is a fundamental equation describing calculating magnetic flux.  F is the "magnetic flux."  E is magnetic field strength in tesla. A is the area in square meters.  is the angle in which an field field penetrates.
 

    Later on, if God allows, I may add future equations for RL, RC, and RLC circuits as well as formulas related to diodes, complex power, and more.
 
 

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