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LITTORAL CÔTE D’OPALE
ElectricityIntroduction
Mathieu Bardoux
IUT du Littoral Côte d’OpaleDépartement Génie Thermique et Énergie
First year
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Summary
1 Electric current
2 Voltage and Power
3 Electrical Resistance
4 Hydraulic Analogy
Mathieu Bardoux (IUTLCO GTE) Electricity First year 2 / 20
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Electric current
Summary
1 Electric currentElectron ?Electric current
2 Voltage and PowerVoltagePower
3 Electrical ResistanceDefinitionJoule effect
4 Hydraulic Analogy
Mathieu Bardoux (IUTLCO GTE) Electricity First year 3 / 20
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Electric current Electron ?
Electron ?
I Elementary particle (light particle or lepton)I Negative electric charge : −e , with e = 1,602176535×10−19 CI Electrons + Protons (charge : e) + Neutrons = Atoms
Mathieu Bardoux (IUTLCO GTE) Electricity First year 4 / 20
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Electric current Electron ?
Atoms : structure and dimensions
10−15 m
10−10 m
Mathieu Bardoux (IUTLCO GTE) Electricity First year 5 / 20
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Electric current Electron ?
Conductors vs Insulators
Conductors : high conductivity / low resistivityI métals (copper, gold, aluminium, iron & alloys)I carbon (graphite, diamond, nanotubes. . . )I water (+ electrolytes)I human bodyI ground
Insulators : low conductivity / high resistivityI glassI porcelainI paperI dry woodI rubberI plastic
Mathieu Bardoux (IUTLCO GTE) Electricity First year 6 / 20
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Electric current Electric current
Electric current
I overall flow of electric chargesI created by the action of electromagnetic forceI carriers : ions or (in most cases) electronsI in electrical networks, a generator produces a charge imbalance⇒ electrons move through a closed loop
Mathieu Bardoux (IUTLCO GTE) Electricity First year 7 / 20
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Electric current Electric current
Current intensity
i =dqdt
By definition, 1A = 1C · s−1
The current is measured using an ammeter connected in series.
A
i
Mathieu Bardoux (IUTLCO GTE) Electricity First year 8 / 20
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Electric current Electric current
Conventions
I Current can be created by positive or negative charge carriers.I Conventional current is arbitrarily defined as a positive charges
flow.I By convention, the electrical current exits the generator through
the positive (+) terminal and returns to the generator through itsnegative (-) terminal.
I Inside the generators, the inverse convention applies.I The conventional direction may differ from the actual direction of
the charge carriers.
Mathieu Bardoux (IUTLCO GTE) Electricity First year 9 / 20
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Electric current Electric current
Propagation rate
I Propagation rate of the electric current in a copper wire :273000 km · s−1
I This is not the speed of electrons (a fraction of millimeter persecond)
I Signal is faster than matter
What distance does an electron travel in domestic network ?
Mathieu Bardoux (IUTLCO GTE) Electricity First year 10 / 20
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Electric current Electric current
Propagation rate
I Propagation rate of the electric current in a copper wire :273000 km · s−1
I This is not the speed of electrons (a fraction of millimeter persecond)
I Signal is faster than matter
What distance does an electron travel in domestic network ?
Mathieu Bardoux (IUTLCO GTE) Electricity First year 10 / 20
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Electric current Electric current
Effects
I HeatingI Chemical decompositionI Mechanical actionI Creation of magnetic fieldsI . . .
Mathieu Bardoux (IUTLCO GTE) Electricity First year 11 / 20
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Voltage and Power
Summary
1 Electric currentElectron ?Electric current
2 Voltage and PowerVoltagePower
3 Electrical ResistanceDefinitionJoule effect
4 Hydraulic Analogy
Mathieu Bardoux (IUTLCO GTE) Electricity First year 12 / 20
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Voltage and Power Voltage
Voltage
I Voltage between two points = work done per unit of chargeagainst a static electric field to move between these points.
I Voltage unit = VoltI 1V = 1J ·C−1
I Notation U (single-phase) or V (three-phase).I Measured with a voltmeter or an oscilloscope connected in
parallel.
V
R
−+U
Mathieu Bardoux (IUTLCO GTE) Electricity First year 13 / 20
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Voltage and Power Power
Electrical power
I Power = Energy per unit of TimeI Power unit = WattI 1W = 1J · s−1 and 1J = 1W · sI Power = flow of EnergyI Electrical power : P = U · I
Mathieu Bardoux (IUTLCO GTE) Electricity First year 14 / 20
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Electrical Resistance
Summary
1 Electric currentElectron ?Electric current
2 Voltage and PowerVoltagePower
3 Electrical ResistanceDefinitionJoule effect
4 Hydraulic Analogy
Mathieu Bardoux (IUTLCO GTE) Electricity First year 15 / 20
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Electrical Resistance Definition
Electrical resistance
I Measurement of the difficulty to pass a current through acomponent
I Leads to a drop in carriers energy when passing through thecomponent
I Unit : OhmI Ohm’s law : U = R · I
Mathieu Bardoux (IUTLCO GTE) Electricity First year 16 / 20
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Electrical Resistance Joule effect
Power dissipation in a resistor : Joule effect
I Conversion of electrical energy into heat.I P = U · II P = R · I 2
I P =U 2
R
Mathieu Bardoux (IUTLCO GTE) Electricity First year 17 / 20
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Hydraulic Analogy
Summary
1 Electric currentElectron ?Electric current
2 Voltage and PowerVoltagePower
3 Electrical ResistanceDefinitionJoule effect
4 Hydraulic Analogy
Mathieu Bardoux (IUTLCO GTE) Electricity First year 18 / 20
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Hydraulic Analogy
Hydraulic AnalogyExample of a waterfall
I Electrical charge⇔ Quantity of waterI Electrical current⇔ Hydraulic volume flow rateI Voltage⇔ Hydraulic head
BFluid particles can move at variable speed
Mathieu Bardoux (IUTLCO GTE) Electricity First year 19 / 20
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Conclusion
ConclusionIn this chapter we have seen. . .
I how electric current is created in conductive materialsI the definitions of fundamental parameters of electric currentI the main properties of resistors
Mathieu Bardoux (IUTLCO GTE) Electricity First year 20 / 20
Electric currentVoltage and PowerElectrical ResistanceHydraulic Analogy
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