1 hvacr114 – electrical for gas heat ohm’s law. 2 german scientist george simon ohm invented...
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HVACR114 – Electrical for Gas Heat
HVACR114 – Electrical for Gas Heat
Ohm’s LawOhm’s Law
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Ohm’s LawOhm’s Law
• German scientist George Simon Ohm invented “Ohm’s Law” by experimenting with electrical circuits, particularly with resistances in these circuits.
• This relationship is called “ Ohm’s Law”
• German scientist George Simon Ohm invented “Ohm’s Law” by experimenting with electrical circuits, particularly with resistances in these circuits.
• This relationship is called “ Ohm’s Law”
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Ohm’s LawOhm’s Law
• Abbreviation’s are used to represent the different electrical factors:
• E= Voltage (electromotive force)
• I= Amperage (current)• R= Resistance ( the
electrical load where the power is consumed.)
• Abbreviation’s are used to represent the different electrical factors:
• E= Voltage (electromotive force)
• I= Amperage (current)• R= Resistance ( the
electrical load where the power is consumed.)
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Ohm’s LawOhm’s Law
• Electrical circuits are sometimes compared to water circuits.
• In a water circuit, pressure pushes the water through the circuit.
• The water flows at a gallon per minute or GPM.• It flows against the resistance of the friction
loss in the pipe and the components in the circuit.
• Electrical circuits are sometimes compared to water circuits.
• In a water circuit, pressure pushes the water through the circuit.
• The water flows at a gallon per minute or GPM.• It flows against the resistance of the friction
loss in the pipe and the components in the circuit.
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• In electrical circuits, the water pressure is compared to Voltage.
• The water volume in gallon per minute is compared to the amperage.
• And, the friction loss in the pipe and components is compared to the resistance to electrical flow in a wire or electrical load.
• In electrical circuits, the water pressure is compared to Voltage.
• The water volume in gallon per minute is compared to the amperage.
• And, the friction loss in the pipe and components is compared to the resistance to electrical flow in a wire or electrical load.
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• Ohm’s Law has determined that the voltage equals the amperage times the resistance.
• E= I x R
• Ohm’s Law has determined that the voltage equals the amperage times the resistance.
• E= I x R
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• The amperage equals the voltage divided by the resistance:
• I= E/R
• The amperage equals the voltage divided by the resistance:
• I= E/R
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• The resistance equals the voltage divided by the amperage:
• R=E/I
• These 3 Formulas can be used to calculate the circuits performance.
• The resistance equals the voltage divided by the amperage:
• R=E/I
• These 3 Formulas can be used to calculate the circuits performance.
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Example:Example:
• Suppose that you measure the resistance (60 ohms) and the current flow (2 amps) of a heating coil in a circuit, and you want to know what the supply voltage should be.
• You use the formula: E=I x R• 2 x 60 = 120volts
• Suppose that you measure the resistance (60 ohms) and the current flow (2 amps) of a heating coil in a circuit, and you want to know what the supply voltage should be.
• You use the formula: E=I x R• 2 x 60 = 120volts
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Another ExampleAnother Example
• Suppose the voltage to a heater is 220 volts and the resistance in the heater is 10 ohms. What should the amperage be when voltage is applied to the unit?
• You use the formula I=E/R to find out.
• 220/10=22 amps
• Suppose the voltage to a heater is 220 volts and the resistance in the heater is 10 ohms. What should the amperage be when voltage is applied to the unit?
• You use the formula I=E/R to find out.
• 220/10=22 amps
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How to get the proper readingHow to get the proper reading
• To measure these readings a Volt- Ohm- multi-meter (VOM) is used.
• The ohm portion of the meter is used to measure the resistance of a component.
• To get the correct ohm reading of a component, it MUST be isolated from the circuit with NO power on.
• To measure these readings a Volt- Ohm- multi-meter (VOM) is used.
• The ohm portion of the meter is used to measure the resistance of a component.
• To get the correct ohm reading of a component, it MUST be isolated from the circuit with NO power on.
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Electrical PowerElectrical Power
• Electrical power is (P) is measured in watts.• A “watt” (W) is the power used when 1
ampere flows with a potential difference of 1 volt.
• Therefore, power can be determined by multiplying the voltage times the amperes flowing in the circuit.
• Electrical power is (P) is measured in watts.• A “watt” (W) is the power used when 1
ampere flows with a potential difference of 1 volt.
• Therefore, power can be determined by multiplying the voltage times the amperes flowing in the circuit.
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• Watts = Volts x Amperes or P= E x I
• Watts = Volts x Amperes or P= E x I
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• A consumer of electrical power pays the electric company according to the number of “kilowatts” used for a certain time span.
• It is usually billed in kilowatt hours or kWh.• A kilowatt is equal to 1000 watts
• A consumer of electrical power pays the electric company according to the number of “kilowatts” used for a certain time span.
• It is usually billed in kilowatt hours or kWh.• A kilowatt is equal to 1000 watts
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• To determine the power being used, divide the number of watts by 1000:
• P= E x I/ 1000
• To determine the power being used, divide the number of watts by 1000:
• P= E x I/ 1000
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MagnetismMagnetism
• Magnets are classified as either permanent or temporary.
• Permanent magnets are used in only a few applications that air-conditioning and refrigeration techs would work with.
• Electromagnets, is a type of temporary magnet used in many electrical components in the HVAC field.
• Magnets are classified as either permanent or temporary.
• Permanent magnets are used in only a few applications that air-conditioning and refrigeration techs would work with.
• Electromagnets, is a type of temporary magnet used in many electrical components in the HVAC field.
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• A magnetic field exists around a wire carrying an electrical current.
• If you loop the wire several times, the magnetic field increases.
• If the wire is wound into a coil, a stronger magnetic field will be created.
• A magnetic field exists around a wire carrying an electrical current.
• If you loop the wire several times, the magnetic field increases.
• If the wire is wound into a coil, a stronger magnetic field will be created.
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• This coil of wire carrying an electrical current is called a “solenoid”.
• This magnetic field can be used to generate electricity and to cause motors to operate.
• This coil of wire carrying an electrical current is called a “solenoid”.
• This magnetic field can be used to generate electricity and to cause motors to operate.
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