Practical Electricity, part 2 Ev I R P OHMS LAW

hFE current gain Skin effect?

Diodes in action chassis Turn Sig chassis

Agenda Voltage Current Resistance Power, Volt Amps Symbology Single Phase Three Phase

Circuits Electric Circuits Consist of Three Parts : – 1. Power Source – Battery, Solar Cell, – 2. Conductors - Connecting Wires – 3. Load - Device such as, Motors, Lights, Heating etc. 3. Load 1. Power Source Source Simplified Circuit 2. Conductors

VOLTAGE TYPES” “VOLTAGE TYPES” STATIC CHEMICAL SOLAR Squirrel Power

Voltage Voltage (EMF Electromotive Force) – Volts (E or V) = Measurement of electrical force or pressure. Similar to pressure. Expressed as Electromotive Force (E) or (emf) in Ohm’s Law. Common Units: Microvolt (uV) = 1/1,000,000 Volt Millivolt (mV) = 1/1000 Volt Volt = 1 Kilovolt (kV) = 1000 Volts

“Difference of Potential” Difference of Potential = – Is the force that causes free electrons to move through a conductor as an electric current is referred to as difference of potential or often shortened to “potential”. Similar to liquid flow there must be a difference in pressure or “differential pressure” or there will be no flow.

Analogy to Liquid Level Valve LiquidPressure Difference of Potential Level “Difference of Potential”

Switch Load PowerSource Difference of Potential Tank A Tank B When a difference in potential exists between two charged bodies that are connected by a conductor, electrons will flow until the two charges are equalized.

“CURRENT” Electric Current = – The flow of electrons through conductive materials when electricity is being converted to useful work. Two Electric Current Types – Direct Current (DC) – Alternating Current (AC)

“CURRENT” Measurement of Amperage (Current Flow) – Amperes or “Amps” (A) = The measurement of current flow through a conductor (wire). – Number of (electrons) that pass through a given point, in a second. Expressed as Intensity (I) in Ohm’s Law – Common Units: – = 1 Amp – Milliamp (mA) = 1/1000 Amp.001A 1 ma – Microamp (uA) = 1/1,000,000 Amp A 1µa

“RESISTANCE” Resistance (Opposition to Current Flow) – Ohm (W) = Measurement of resistance in an electrical circuit. Similar to restriction of liquid or gas flow. Expressed as Resistance (R) in Ohm’s Law. Common Units: Ohms (W) = 1 Ohm Kilohms (k W) = 1000 Ohms Megohms (meg W) = 1,000,000 Ohms Every load on an electrical circuit creates resistance. Resistance to the current load creates heat.

The OHM CURRENT RATING WIRE SIZE (known as ‘gauge’) WIRE DIAMETER (expressed in circular mils*) 30 Amps10 AWG Amps12 AWG Amps14 AWG Amps16 AWG Amps18 AWG1620 *Circular Mils = the standard unit of measurement of a round wire cross- sectional area The area in circular mils of a round conductor is obtained by squaring the diameter, measured in mils.

Ohms Per Foot

“IMPEDANCE, DC ” IMPEDANCE – Algebraic sum of all the Resistance in the circuit. For DC = Z is the same as the total resistance of the circuit ( Rt ) Z

Resistance and Voltage Drop 1000 ft. 100 Psig Psig 1” Pipe Psig water pressure - 1 GPM flow Pressure Drop Voltage Drop 100 Volts Volts 12 Gage Wire Volts - 1 Amp Current flow 1000 ft. “VOLTAGE DROP”

Power In Back to the Future, Doc Emit Brown declares that it takes 1.21 gigawatts to travel through time. The gigawatt is a unit of power, not energy. Now, a gigawatthour is a unit of energy.

“POWER” “WATT” Electrical Power (Horsepower) – Watt (W) = 1 Watt = 1 Volt times 1 Amp of current Expressed as (P) in power calculation formulas. 746 Watts = 1 Horsepower. 1 HP = ¾ KiloWatt Common Units: 1 Microwatt = 1/1,000,000 Watt 1 Milliwatt = 1/1000 Watt 1 Kilowatt = 1000 Watts 1 Megawatt = 1,000,000 Watts 1 GigaWatt = 1 Billion Million Watts Kilowatt Hour = Kilowatts used in 1 hour

Review Discussion – Voltage is a measurement of: electrical force (similar to pressure) – Amperage is a measurement of current flow (similar to flow) – Ohm is a measurement of resistance to current flow (similar to restriction) – Wattage is a measurement of power used to perform work (horsepower)~ – Voltage Drop is the result of the corresponding result of opposition to current flow.

2 More Electrical Terms Inductance (Coil, transformer) Capacitance (Capacitor) Factors present in an AC circuit because the current is operating at 60 HZ, frequency dependant. X L = 2π f L 1 X C = 2π f C

AC Current Relationships Current thru Resistor is in phase Current thru Inductor will lag 90 Current thru Capacitor will lead by 90 Magnitude of current thru RLC will dependent on Impedance which is a vector sum POWER FACTOR CORRECTION – Capacitor Banks

Resistive vs Inductive ELI ICE MAN Voltage leads Current in a inductive circuit Current leads voltage in a capacitive circuit

Electrical Theory Basic Formulas - Ohm’s Law Law 1 -If the voltage remains constant the current is inversely proportional to the resistance Law 2 - If the current remains constant the emf voltage across a device varies directly with the resistance Law 3 - If the resistance remains constant the current varies directly with the applied voltage V = EMF in Volts I = Intensity in Amps R = Resistance in Ohms I V R

Symbols

Electrical Theory Basic Formulas - Calculating Power – The basic formulas used for calculating power as it is related to volts of emf, Amps of current. and resistance are contained in the following summary pie graph. P = Power in Watts I = Intensity in Amps V = EMF in Volts P = I x V I P V

Electrical Theory Summary of Basic Formulas

Calculate Voltage Using Ohms Law

Calculate Resistance Using Ohms Law

Calculate Current Using Ohms Law

Handout

Calculate Resistance (Handout) Resistors in series Resistors in parallel Resistors in combination

Calculate Current Current is same in series (Rt) Current in parallel adds (Rt)

Calculate Power Power Adds in parallel

Voltage Drop

Symbology Wires, Not Connected, Crossing Wires, Connected, Crossing

LADDER LOGIC

ELECTRIC DRYER

BUILDINGS BLUEPRINT

Solar Cell Battery Regulator

AC Single Phase

AC 3 Phase 3 Coils in Generator Cycles are 120 degrees apart A B C ABCA

Advantages of 3 PH AC 3 or 4 Wires Depending on Load Wire is Expensive, but will be smaller

3 PH - WYE Connected Load

Power in Delta & Y Connected Systems Power = √3 * E * I * pf DELTA Y WYE WYE Neutral Current Occurs ONLY when Phase current is unbalanced

Battery Configurations

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