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Home , Georg Ohm

Electrical Basics

Power & ’s Law Group 1

• Work together to understand the informaon in your secon. • You will have 10 minutes to review the material and present it to the class. • 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 • 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 .

• This “pressure” is sometimes referred to as “” or EMF. • Voltage is represented by the symbol E

4 • 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 Ω

5 • 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 "“.

(French Charles Augustin de Coulomb in 1780’s)

6 • 1 coulomb = 6.24 x 1018 electrons = 6,240,000,000,000,000,000 = more than 6 billion billion electrons!

If 1 coulomb of electrons go by each second, then we say that the current is 1 "" or 1 amp

(Named after André-Marie Ampère, 1826)

7 • Voltage is measured in . • A voltage of 1 means that 1 "" 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 )

8 • Resistance is measured in ohms.

• Symbolized with the letter “R” or with the symbol “Ω”

(Named after the German physicist Georg Ohm, 1827)

9 l Conductor v Allows the Flow of Electrons l - v Stops/ Minimizes the Flow of Electrons l 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 direcon l Capacitor v Stores excess voltage l Shunt v Redirects the Flow of Electrons when triggered

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• Standard Test Conditions (STC) A set of reference measurement conditions. (25° C, or 77° F, 1000 W/m2, AM1.5 (air mass) )

• 1 Meter = 3.28 Feet

• 1 cm = .3937 Inches

• 1 Amp x 1 Volt = 1 (Power)

• 1 HP = 746

• Standard Operating Conditions (NOC) A more realistic set of reference conditions. (25° C or 77° F, 800 W/m2, 1 m/s wind speed)

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• Degrees = (1.8 x C°) + 32

• Degrees = (F° – 32) x 0.555

• 1 Langley = 2.065 W/m2 (Unit of energy distribution over an area. This unit is used to measure solar irradiation or “insolation”.

• 1 kWh/m2 = 3.6 MJ/m2

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Group 2

• Work together to understand the informaon in your secon. • You will have 10 minutes to review the material and present it to the class. 14 How is resistance, voltage, & current related?

E = I R

Or…

E = I x R where: E = voltage in volts I = current in amps R = resistance in ohms

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“milli” = 1/1000 So a milli-Amp Using E = I R Is 1/1000 of an amp

1mA = 1/1000A E = .003 (I) x 3,000 (R) or .001A E = 9 volts (or 9 v)

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• What if you know the voltage & resistance but not the current?

• What if you know the voltage & current but not the resistance?

17 • Knowing any 2 values, E, I, or R one can find the 3rd 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 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

“k” = 1000 So… 3k = 3,000 3kA = 3,000 amps R = E / I 3kV = 3,000 volts 3 kΩ = 3,000 ohms

R = 9 (E) / .003 (I)

R = 3,000 ohms (or 3k ohms or 3k Ω)

20 I = E / R

I = 9 (E) / 3,000 (R)

I = .003 amps (or .003A or 3 milliamps or 3 mA)

21 • 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 23 Group 3

• Work together to understand the informaon in your secon. • You will have 10 minutes to review the material and present it to the class.

l Somemes 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.

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

• 1 watt = 1 joule per second.

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Remember…

• Voltage “V” tells us the number of per coulomb

• Current tells us the number of per second

So…

Power = number of watts = number of joules/second = joules/coulomb x coulombs/second = V x I

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Or the power formula…

P = I x V

Or

P = IV

Where P = power in watts (W) I = current in amps (A) V = voltage in volts (V)

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

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

29 • Knowing any 2 values, P, I, or E, one can find the 3rd 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 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

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• Additional Power Formulas

32 Group 4

• Work together to understand the informaon in your secon. • You will have 10 minutes to review the material and present it to the class. SERIES DC CIRCUITS & PARALLEL DC CIRCUITS

34 • Two basic ways to connect more than two circuit components: series & parallel.

• These components can be electronic components such as & 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 (mA)

150 mA 150 mA 150 mA 150 mA 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 mA 150 mA 150 mA 150 mA

38 Series Power Sources

150 mA

Each cell?

39 Series Power Sources

Total?

Each solar panel = 4 VDC @ 100mA

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 1.5 VDC 1.5 VDC 150 mA 150 mA 150 mA

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 1.5 VDC 1.5 VDC 150 mA 150 mA 150 mA

43 Parallel Circuits

600 mA

Each cell?

44 Parallel Circuits

Total?

Each solar panel = 4 VDC @ 100mA 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 @ 100mA 48 RULE SUMMARY: Series Circuits

1. The total output current (measured in amps) is equal to the individual power source.

3. The total output voltage (measured in volts) is equal to the sum of the individual power sources.

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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.

3. The total output voltage (measured in volts) is equal to the voltage of the individual power sources.

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Group 5

• Work together to understand the informaon in your secon. • You will have 10 minutes to review the material and present it to the class. FORMULA SUMMARY

Ohm’s Law:

E = I * R

I = E / R

R = E / I

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FORMULA SUMMARY

Power:

P = I x E P = I2 x R

I = P / E P = E2 / R

E = P / I

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FORMULA SUMMARY

Resistance in a Series Circuit:

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FORMULA SUMMARY

Resistance in a Parallel Circuit:

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