Electricity Primer Projects

Work is a force times a displacemnt. The simpelest example is when lifts an object weighing one pound one foot. One foot pound of work is done. Also a torque times an angular displacement is work. Another example is when a pressure moves a volume of gas or liquid. Electric charge is just like matter or energy, it is not created or destroyed. Maslama al-Majriti in Al-Andalus(later called Iberia) first established conservation of mass about 1000 CE. (later by Lavoisier ) The conservation of energy was established by Count Rumford, who studied the mechanical equivalent of heat while boring out cannons. He also invented the double boiler and percolator coffee pot. Kirchhoff's Law is the conservation of electric charge. Gustav Kirchhoff was from Konigsberg. The electromotive force or voltage in units of Volts is the force. The force moves or displaces the charge at a rate of current in units of Amperes. Ohm's law is that a resistance, in units of Ohms, opposes the flow of current with a force or voltage equal to the flow or current in units of Amperes times the resistance in units of Ohms.

` E=IR ` ` P=I^2 R `

` W=Pt `

where E is in Volts, P is in Watts, I is in Amperes, R is in Ohms, W is in Watt hours, t is in hours,

` I_1 = \sqrt(P/R) `

Now taking a great leap to equations found in the National Electrical Code, an expression relating to the power required by multiple welders with a duty cycle factor X is:

` I_e = \sqrt(I_1^2*X - I_0^2*(1-X) ) ` ref: NEC2008, NFPA Quincy MA, 630.12(B)

An expression relating to the time and temperature of insulation:

` (I^2/A^2)t = 0.0125*log_10((T_2+228)/(T_1 -228)) ` ref: NEC2008 240.92(B)(2)

A battery that has internal resistance will exhibit voltage drop when increased current is drawn. A standard is the No. 6 ignition dry cell can have an internal resistance of 0.02 Ohms and an initial, flash amperage, current of 26 Amperes.

POWER LIMITED CLASSES

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A 12 Volt lead acid battery used in an automobile can deliver 180 Watts/kg or a 450 A flash current. detailed voltage,current,power,impedance diagram  

The way in which the three wires with 3 phase power are connected to 3 phase motors effects the direction in which the motor turns. Attempts to coordinate this in more than one building, to enable cord and plug movement require some standardization and measurement. Definitions and conventions,e.g. NEC2008 409.102,408.3(E),as well are needed. The conventions even when consistent vary in different   parts of the   world.   ( t=9766 )   The conventions for motor winding hookup   (id=45 Itemid=74)   for wye,delta and multivoltage are the same everywhere. Three phase power can be derived from two phase power but not without an idler motor or and active compensating device or reactive devices that have to be adjusted for the amount of power required.

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