GRATUITOUS QUICK REVIEW

"THIS WILL HURT ME MORE THAN IT HURTS YOU."

WHY IS POWER = I^{2} R ?

CURRENT IS "I,' OR "INTENSITY," IN AMPERES

VOLTAGE IS "E," OR "ELECTROMOTIVE FORCE," IN VOLTS

RESISTANCE IS "R" OR RESISTANCE IN FRENCH, IN OHMS.

ELECTRICAL CURRENT THROUGH A CIRCUIT IS PROPORTIONAL TO THE APPLIED VOLTAGE AND INVERSELY PROPORTIONAL TO THE CIRCUIT RESISTANCE. THIS IS OYHM'S LAW, I = E / R

THIS IS INTUITIVE, LIKE VOLUME OF WATER THROUGH A PIPE DEPENDS ON THE PRESSURE AND THE RESISTANCE OF THE PIPE.

POWER IS VOLTAGE TIMES CURRENT, OR E TIMES I, WHERE VOLTAGE IS THE PRESSURE, AND NUMBER OF ELECTRONS PER SECOND INCLUDES THE TIME INVOLVED, JUST LIKE IN

1 HORSEPOWER = 550 POUNDS RAISED A FOOT IN ONE SECOND. (550 FOOT-POUNDS PER SECOND).

THAT IS, POWER IS THE AMOUNT OF WORK DONE IN THE TIME INVOLVED.

FOR ELECTRICITY, POWER IS THE NUMBER OF ELECTRONS PER SECOND (AMPERES) TIMES THE PRESSURE (VOLTAGE) INVOLVED.

EXTRA CREDIT: NUMBER OF ELECTRONS IS MEASURED IN "COULOMBS." A COULOMB IS 6.2415 × 10^{18} ELECTRONS (OR OTHER CHARGES). SO ONE AMPERE IS 6.2415 × 10^{18} ELECTRONS PER SECOND. AND THERE'S YOUR TIME ELEMENT FOR "POWER," EMBEDDED IN THE CURRENT MEASUREMENT.

SO HOW DID "POWER" BECOME I^{2}R?

I = E / R OHM'S LAW

I X R = E BY TRANSPOSING

P = E X I

SUBSTITUTING I X R FOR E,

P =I X R x I

THAT IS,

P=I^{2}R

Terry, 230RN

Note the units have changed names recently. This demonstrates the concept in our old units.