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TitleElectrical Formulas Explanations
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Total Pages16
Table of Contents
                            HEAT
UNITS DERIVED FROM THE BASE ELECTRICAL UNIT (AMPERE)
RULES OF THUMB FOR ELECTRICAL MOTORS
ELECTRICAL FORMULAS
	Inductive reactance XL
	Capacitive reactance XC
TRIGONOMETRY
POWER FACTOR CORRECTION TABLE:
TRANSFORMER CALCULATIONS
VOLTAGE AND CURRENT RELATIONSHIPS
VOLTAGE AND COIL TURN RELATIONSHIPS
AMPERES AND COIL TURN RELATIONSHIPS
RESISTOR COLOR CODE
FULL-LOAD CURRENT IN AMPERES FOR DIRECT-CURRENT MOTORS
COMPARISON OF AC AND DC CURRENTS
PREFIXES USED FOR SUBDIVISIONS AND MULTIPLES OF UNITS
                        
Document Text Contents
Page 8

Electrical Formulas, Explanations

Impedance (Z)

Impedance is the total opposition to an alternating current presented by a circuit (OHMS). Total AC
resistance.

Amperes

Volts

I

E
Z == , ( ) 22)(Im CL XXRZpedance −+=

Power factor (PF)

Power factor (Pf) equals the cosine, where θ is the angle is either lead or lag.

Z

R

EI

P

werApparentPo

TruePower
PF ===

TRIGONOMETRY

Trigonometry is the mathematics dealing with the relations of sides and angles of triangles. A triangle is a
figure enclosed by three straight sides. The sum of the three angles is 180 degrees. All triangles have six
parts: three angles and three sides opposite the angles. Right triangles are triangles that have one angle of
ninety degrees and two angles of less than ninety degrees.

Hypotenuse

deOppositeSi
Sine =θ

Hypotenuse

deAdjacentSi
CoSine =θ

deAdjacentSi

deOppositeSi
Tangent =θ

deOppositeSi

deAdjacentSi
CoTangent =θ

deAdjacentSi

Hypotenuse
Secant =θ

deOppositeSi

Hypotenuse
CoSecant =θ

Note: θ = Theta = any angle

Remember: SOHCAHTOA, Sine, opposite, hypotenuse, cosine, adjacent, hypotenuse, tangent,
opposite, adjacent.

Page 8 of 16

ADJACENT SIDE

HYPOTENUSE

O
P

P
O

S
IT

E
S

ID
E

60º

90º30º

“Y”

“X”

ALWAYS PLACE THE ANGLE TO BE SOLVED AT
THE VERTEX (WHERE “X” AND “Y” CROSS).

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