Electrical Basics Power Ohms Law Group 1 Work

Electrical Basics Power & Ohm’s Law

Group 1 • Work together to understand the information in your section. • You will have 10 minutes to review the material and present it to the class.

Current • With some applied force, electrons will move from a negatively charged atom to a positively charged atom. This flow of electrons between atoms is called current. • Current is represented by the symbol I 3

Voltage • When there is a lack of electrons at one end of a conductor and an abundance at the other end, current will flow through the conductor. This difference in “pressure” is referred to as voltage. • This “pressure” is sometimes referred to as “electromotive force” or EMF. • Voltage is represented by the symbol E 4

Resistance • Resistance is the opposition to the flow of electrons (aka “current”). • Every material offers some resistance. • Conductors offer very low resistance. • Insulators offer high resistance. • Resistance is represented by the Symbol R • Resistance is measured in Ohms Ω 5

Measuring Current • Current is measured by literally counting the number of electrons that pass a given point. • Current will be the same at any point of a wire. • The basic unit for counting electrons is the "coulomb“. (French physicist Charles Augustin de Coulomb in 1780’s) 6

Measuring Current (cont) • 1 coulomb = 6. 24 x 1018 electrons = 6, 240, 000, 000 = more than 6 billion electrons! If 1 coulomb of electrons go by each second, then we say that the current is 1 "ampere" or 1 amp (Named after André-Marie Ampère, 1826) 7

Measuring Voltage • Voltage is measured in volts. • A voltage of 1 volt means that 1 "Joule" of energy is being delivered for each coulomb of charge that flows through the circuit. • A “Joule” is the basic unit of energy in the metric system - its about the amount of energy it takes to lift two pounds a height of 9 inches. (Named after James Prescott Joule) 8

Measuring Resistance • Resistance is measured in ohms. • Symbolized with the letter “R” or with the symbol “Ω” (Named after the German physicist Georg Ohm, 1827) 9

Key Terms l Conductor v Allows the Flow of Electrons l Insulatorv Stops/ Minimizes the Flow of Electrons l Resistor v Resists the Flow of Electrons l Semi-Conductor v Acts as both a Conductor / Insulator l Diode v Stops the flow of Electrons in one direction l Capacitor v Stores excess voltage l Shunt v Redirects the Flow of Electrons when triggered 10

Key Conversions • Standard Test Conditions (STC) A set of reference measurement conditions. (25° C, or 77° F, 1000 W/m 2, AM 1. 5 (air mass) ) • 1 Meter = 3. 28 Feet • 1 cm =. 3937 Inches • 1 Amp x 1 Volt = 1 Watt (Power) • 1 HP = 746 Watts • Standard Operating Conditions (NOC) A more realistic set of reference conditions. (25° C or 77° F, 800 W/m 2, 1 m/s wind speed) 11

Key Conversions • Degrees Fahrenheit = (1. 8 x C°) + 32 • Degrees Celsius = (F° – 32) x 0. 555 • 1 Langley = 2. 065 W/m 2 (Unit of energy distribution over an area. This unit is used to measure solar irradiation or “insolation”. • 1 k. Wh/m 2 = 3. 6 MJ/m 2 12

Group 2 • Work together to understand the information in your section. • You will have 10 minutes to review the material and present it to the class.

OHM’S LAW 14

Ohm’s Law How is resistance, voltage, & current related? E=IR Or… E=Ix. R where: E = voltage in volts I = current in amps R = resistance in ohms 15

Ohm’s Law “milli” = 1/1000 Using E = I R E =. 003 (I) x 3, 000 (R) E = 9 volts (or 9 v) So a milli-Amp Is 1/1000 of an amp 1 m. A = 1/1000 A or. 001 A 16

Ohm’s Law • What if you know the voltage & resistance but not the current? • What if you know the voltage & current but not the resistance? 17

Ohm’s Law • Knowing any 2 values, E, I, or R one can find the 3 rd one by simple algebraic manipulation of the formula E= I x R • DEFINITIONS: >An arithmetic operation is +, -, x, or ÷ >The opposite operation of: + is – x is ÷ - is + ÷ is x 18

Ohm’s Law To manipulate the formula E = I / R… RULE: Whatever arithmetic operation is done to one side of the equation must be done to the other side. So… E = I x R Becomes… I = E / R or R = E / I 19

Ohm’s Law “k” = 1000 So… 3 k = 3, 000 3 k. A = 3, 000 amps R = E / I 3 k. V = 3, 000 volts 3 kΩ = 3, 000 ohms R = 9 (E) /. 003 (I) R = 3, 000 ohms (or 3 k ohms or 3 k Ω) 20

Ohm’s Law I = E / R I = 9 (E) / 3, 000 (R) I =. 003 amps (or. 003 A or 3 milliamps or 3 m. A) 21

Ohm’s Law (cont) • For those who are not comfortable with algebra, there's a trick to remembering how to solve for any one quantity, given the other two. . . 22

Ohm’s Law (cont) 23

Group 3 • Work together to understand the information in your section. • You will have 10 minutes to review the material and present it to the class.

Power l Sometimes we want to know the rate at which energy is delivered, not how much energy is delivered per coulomb of charge. l The rate at which energy is delivered is called power. l Power is defined as: Power = Energy / Time. 25

Power • The unit of power corresponding to 1 joule per second is called a “watt”. • 1 watt = 1 joule per second. 26

Power Remember… • Voltage “V” tells us the number of joules per coulomb • Current tells us the number of coulombs per second So… Power = number of watts = number of joules/second = joules/coulomb x coulombs/second = V x I 27

Power Or the power formula… P=Ix. V Or P = IV Where P = power in watts (W) I = current in amps (A) V = voltage in volts (V) 28

Power • What if you know the power & voltage but not the current? • What if you know the power & current but not the voltage? 29

Power • Knowing any 2 values, P, I, or E, one can find the 3 rd one by simple algebraic manipulation of the formula P=I E • DEFINITIONS: >An arithmetic operation is +, -, x, or ÷ >The opposite operation of: + is – x is ÷ - is + ÷ is x 30

Power To manipulate the formula P = I x E… RULE: whatever arithmetic operation is done to one side of the equation must be done to the other side. So… P = I x E Becomes… I = P / E or E = P / I 31

Power • Additional Power Formulas 32

Group 4 • Work together to understand the information in your section. • You will have 10 minutes to review the material and present it to the class.

SERIES DC CIRCUITS & PARALLEL DC CIRCUITS 34

What are “series” & “parallel” circuits? • Two basic ways to connect more than two circuit components: series & parallel. • These components can be electronic components such as resistors & capacitors or they can be power sources such as batteries, solar cells, or solar modules. 35

SERIES CIRCUITS • The defining characteristic of a series power circuit is that there is only one path for electrons to flow. • The power sources are connected end-to-end in a line to form a single path for electrons to flow… 36

Series Rule #1 • The total output current (measured in amps) is equal to the individual power source. “milli” = 1/1000 So a milli-amp (m. A) 150 m. A Is 1/1000 of an amp 37

Series Rule #2 The total output voltage (measured in volts) is equal to the sum of the individual power sources. 150 m. A 38

Series Power Sources 150 m. A Each cell? 39

Series Power Sources Total? Each solar panel = 4 VDC @ 100 m. A 40

Parallel Circuits • The defining characteristic of a parallel power circuit is that all the positive terminals are connected together and all the negative terminals are connected together… 41

Parallel Circuits Parallel Rule #1 • The total output current (measured in amps) is equal to the sum of the currents of the individual power sources. 1. 5 VDC 150 m. A 42

Parallel Circuits Parallel Rule #2 • The total output voltage (measured in volts) is equal to the voltage of the individual power sources. 1. 5 VDC 150 m. A 43

Parallel Circuits 600 m. A Each cell? 44

Parallel Circuits Total? Each solar panel = 4 VDC @ 100 m. A 45

Series or Parallel? 46

SERIES / PARALLEL CIRCUITS • We can have circuits that are a combination of series and parallel to increase both amperage (current) and voltage… 47

SERIES / PARALLEL CIRCUITS Each solar panel = 4 VDC @ 100 m. A 48

RULE SUMMARY: Series Circuits 1. The total output current (measured in amps) is equal to the individual power source. 2. The total output voltage (measured in volts) is equal to the sum of the individual power sources. 49

RULE SUMMARY: Parallel Circuits 1. The total output current (measured in amps) is equal to the sum of the currents of the individual power sources. 2. The total output voltage (measured in volts) is equal to the voltage of the individual power sources. 50