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E1 – Electrical Fundamentals # 1 - Atoms and Electrons, Ohms Law, and Resistance

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© 2005 Refrigeration Training Services - E1#1 Atoms,Electron,Ohms Law,Resistance v1.0 2 Atoms Nucleus: the center –Made up of neutrons and protons Neutrons –Neutral particles –Neither positive nor negative Protons –Positively charged particles Electrons –Negatively charged particles –Orbit around the nucleus 8+ 8n 1 Oxygen atom

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© 2005 Refrigeration Training Services - E1#1 Atoms,Electron,Ohms Law,Resistance v1.0 3 Molecules Atoms can combine to form molecules

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© 2005 Refrigeration Training Services - E1#1 Atoms,Electron,Ohms Law,Resistance v Hydrogen atom 1 proton 1 electron n 1 Oxygen atom 8 protons 8 neutrons 8 electrons 1 Molecule of Water 2 Hydrogen+ 1 Oxygen = H2OH2O n 1 Hydrogen atom 1 proton 1 electron 1+ Molecules

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© 2005 Refrigeration Training Services - E1#1 Atoms,Electron,Ohms Law,Resistance v1.0 5 Positive and Negative Charges Balanced charge: electrons equal protons Unbalanced charge: allows electrons to flow –Negative charge: more electrons than protons –Positive charge: less electrons than protons

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© 2005 Refrigeration Training Services - E1#1 Atoms,Electron,Ohms Law,Resistance v Protons and 10 Electrons Neutral n Balanced Charge

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© 2005 Refrigeration Training Services - E1#1 Atoms,Electron,Ohms Law,Resistance v Protons and 9 Electrons Positive n Positively Charged Molecule

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© 2005 Refrigeration Training Services - E1#1 Atoms,Electron,Ohms Law,Resistance v Protons and 11 Electrons Negative n Negatively Charged Molecule

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© 2005 Refrigeration Training Services - E1#1 Atoms,Electron,Ohms Law,Resistance v1.0 9 Conductors Free electrons easily leave their orbits Materials with free electrons are conductors Copper atoms have a free electron

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© 2005 Refrigeration Training Services - E1#1 Atoms,Electron,Ohms Law,Resistance v Copper Atom Nucleus of neutrons and protons Valence or free electron 29 electrons

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© 2005 Refrigeration Training Services - E1#1 Atoms,Electron,Ohms Law,Resistance v Current flow in a Conductor Free electrons can be forced to move from atom to atom by: 1.Friction – Static electricity 2.Chemical – Batteries 3.Magnetic (induction) - Generator

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© 2005 Refrigeration Training Services - E1#1 Atoms,Electron,Ohms Law,Resistance v Copper is a good conductor Current flow through copper Empty space attracts free electron Voltage knocked electron free

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© 2005 Refrigeration Training Services - E1#1 Atoms,Electron,Ohms Law,Resistance v OHMs Law 1 volt will push 1 amp through 1 ohm of resistance Electromotive force = I ntensity x Resistance E = I x R E = I R –Electromotive force (E) = Volts – I ntensity ( I ) = Amps –Resistance (R) = Resistance in Ohms (Ω) Note: E = I x R can also be expressed as Volts = Amps x Resistance

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© 2005 Refrigeration Training Services - E1#1 Atoms,Electron,Ohms Law,Resistance v Using Ohms Law Equation 1.E = I x R (Volts = Amps x Resistance) 2.Solving for I, divide R into E: E R = I, or E/R = I 3.Solving for R, divide I into E: E I = R, or E/ I = R

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© 2005 Refrigeration Training Services - E1#1 Atoms,Electron,Ohms Law,Resistance v Intro to the Math Behind Ohms Law 2=205x x You may divide both sides of an equation by any number (except 0.) =205 x = = x 5

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© 2005 Refrigeration Training Services - E1#1 Atoms,Electron,Ohms Law,Resistance v =amps5x The Math Behind OHMs Law # 1 E=IRx E = I x R For example: 10 volts = (2 amps) x (5 ohms) Solve for I: Solve for amps: R R 10=ohms2x E=IRx Solve for R: Solve for ohms: 225 I I Solve for E: Solve for volts: E=Ix R volts=2x 510

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© 2005 Refrigeration Training Services - E1#1 Atoms,Electron,Ohms Law,Resistance v =amps5 x The Math Behind OHMs Law #2 E=IR x 10=2ohms x E=IR x Solve for I: Solve for amps: Solve for ohms: Solve for R: E = I x R For example: 10 volts = (2 amps) x (5 ohms) 2 5 Solve for E: Solve for volts: E=Ix R volts=2x 510

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© 2005 Refrigeration Training Services - E1#1 Atoms,Electron,Ohms Law,Resistance v What is the voltage supplied to the following circuit? E = I R Solve for E (voltage): E = 5 amps x 24 Ω E = 5 x 24 E = 120 volts R = 24 Ω I = 5 amps E = ? V Ohms Law Example 1:

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© 2005 Refrigeration Training Services - E1#1 Atoms,Electron,Ohms Law,Resistance v Ohms Law Example 2: E = IR Solve for I (intensity in amps): E R = I 120 v 10 Ω = ? amps = 12 amps R = 10 Ω I = ? amps E = 120 V What is the current (intensity in amps) in the following circuit?

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© 2005 Refrigeration Training Services - E1#1 Atoms,Electron,Ohms Law,Resistance v What is the resistance (ohms) of the load below? E = IR Solve for R (Resistance in ohms): E I = R 120 v.83 amps = ? Ω = 145 Ω R = ? Ohms Ω I =.83 amps E = 120 V Ohms Law Example 3:

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© 2005 Refrigeration Training Services - E1#1 Atoms,Electron,Ohms Law,Resistance v Ohms Law Disc Using a disc is another way to solve the Ohms Law equation

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© 2005 Refrigeration Training Services - E1#1 Atoms,Electron,Ohms Law,Resistance v E RI I = Intensity (Amps) OHMs Law Disc R = Resistance (OHMS ) E = Electromotive Force (Volts)

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© 2005 Refrigeration Training Services - E1#1 Atoms,Electron,Ohms Law,Resistance v E=I x R R= E I OHMs Law Disc I= E R To find Voltage E RI To find Current To find Resistance

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© 2005 Refrigeration Training Services - E1#1 Atoms,Electron,Ohms Law,Resistance v E RI To find Resistance R =R = E I E R I To find Current I =I = E R E RI To find Voltage E = I x R E RI E = Electromotive Force (Volts) I = Intensity (Amps) R = Resistance (OHMs ) Reviewing OHMs Law Disc

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© 2005 Refrigeration Training Services - E1#1 Atoms,Electron,Ohms Law,Resistance v Calculating Electrical Power Power is the rate at which work is done. Power = Intensity x Electromotive force P = I E Power (watts) = Amps x Volts

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© 2005 Refrigeration Training Services - E1#1 Atoms,Electron,Ohms Law,Resistance v Ohms Law Example 4: Power (watts) = Amps x Volts Power = I ntensity x Electromotive force P = I E P = 15 amps x 120 volts P = 15 x 120 P = 1800 Watts Example 4: What is the power consumption of an electric circuit using 15 amperes and 120 volts?

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© 2005 Refrigeration Training Services - E1#1 Atoms,Electron,Ohms Law,Resistance v Power (watts) = Amps x Volts Power = I ntensity x Electromotive force P = I E solve for I P E = I 4800 watts 240 volts = I (amps) = 20 Amps Ohms Law Example 5: Example 5: What is the current of an electric heater rated at 4800 watts on 240 volts?

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© 2005 Refrigeration Training Services - E1#1 Atoms,Electron,Ohms Law,Resistance v Power = Amps 2(squared) x Ohms Power = I ntensity 2 x Resistance P = I 2 R P = 5 2 amps x 10 ohms P = 5 2 x 10 P = 25 x 10 P = 250 Watts Ohms Law Example 6: Example 6: What is the power of an electric circuit with 5 amps current and 10 ohms resistance?

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© 2005 Refrigeration Training Services - E1#1 Atoms,Electron,Ohms Law,Resistance v Ohms Law Wheel All applications of Ohms Law formulas can be represented as the spokes of a wheel.

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© 2005 Refrigeration Training Services - E1#1 Atoms,Electron,Ohms Law,Resistance v P is Power in WattsI is Intensity in Amps R is Resistance in OhmsE is Electromotive force in Volts I2 RI2 R P.IP.I E2RE2R ERER PEPE E.IE.I E2PE2P IE IR PI2PI2 PRPR PR P E I R Ohms Law Wheel

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© 2005 Refrigeration Training Services - E1#1 Atoms,Electron,Ohms Law,Resistance v Resistance & Loads Resistance: –Opposition to electron flow in the circuit –Measured in ohms (Ω) Loads: –Must have some resistance –Provide a path for electron flow

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© 2005 Refrigeration Training Services - E1#1 Atoms,Electron,Ohms Law,Resistance v Compare resistance to crossing a river Resistance is the open space between the shores Cars represent electrons Bridges represent loads Without bridges there is no way the cars can cross This is known as infinite resistance

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Go Team! © 2005 Refrigeration Training Services - E1#1 Atoms,Electron,Ohms Law,Resistance v Infinite Resistance

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© 2005 Refrigeration Training Services - E1#1 Atoms,Electron,Ohms Law,Resistance v A load is added The load provides a path for electrons There is still high resistance to flow But it is no longer infinite resistance

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Go Team! © 2005 Refrigeration Training Services - E1#1 Atoms,Electron,Ohms Law,Resistance v But there is still High Resistance A small load provides a path for some of the electrons

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© 2005 Refrigeration Training Services - E1#1 Atoms,Electron,Ohms Law,Resistance v More load is added Less resistance More electron flow

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Go Team! © 2005 Refrigeration Training Services - E1#1 Atoms,Electron,Ohms Law,Resistance v The resistance is lower Lower resistance means more electrons, or current flow.

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© 2005 Refrigeration Training Services - E1#1 Atoms,Electron,Ohms Law,Resistance v Low or no resistance can be bad The lower the resistance, –The higher the electron flow If the current flow is out of control, –The circuit is overloaded

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Go Team! © 2005 Refrigeration Training Services - E1#1 Atoms,Electron,Ohms Law,Resistance v Overload OVERLOAD

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© 2005 Refrigeration Training Services - E1#1 Atoms,Electron,Ohms Law,Resistance v Resistance, Watts, and Amps Load resistance affects amps and watts The lower a loads resistance, The higher its amps and watts

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© 2005 Refrigeration Training Services - E1#1 Atoms,Electron,Ohms Law,Resistance v Infinite Resistance Ohms (R) OPEN Circuit Breaker Trips No Watts (P) No Amps (I) 10 W 1500 Ohms.08 A 100 W 150 Ohms.8 A 8 A 1000 W 15 Ohms BOOM L1N High Watts & High Amps 0 Ohms (Note: approximate values in an alternating current 120v circuit) How Resistance affects Amps and Watts

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© 2005 Refrigeration Training Services - E1#1 Atoms,Electron,Ohms Law,Resistance v1.0 42

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