e4 introducing electricity part 3
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E4C
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PTER
Introduction to Electricity
Watch this video
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E4C
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PTER
Introduction to Electricity
• For electricity to flow in a circuit, electrons in the copper atoms of the wires must move from one atom to the next.
• This flow of electron in one direction in a circuit is called an electric current.
What is an electric current?What is an electric current?
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E4C
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PTER
Introduction to Electricity
Electron flow in a circuitElectron flow in a circuit
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Introduction to Electricity
• Energy is needed for the electron to move.
• Source of energy: electric cell in the circuit
• Electric cell has:- a positive terminal, and- a negative terminal
• Electrons flow out of the negative terminal of the electric cell, round the circuit and back to the positive terminal of the cell.
Path of electron flowPath of electron flow
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E4C
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PTER
Introduction to Electricity
• Have you heard of ‘static’ electricity?• It is produced when certain materials, like wool and
plastics, are rubbed against each other. • The rubbing process caused electrons from the surfaces
of one materials to be transferred to the surface of the other material.
• Have you experienced a shock from static electricity before? Recall how the static electricity could have been produced.
Do you know?Do you know?
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E4C
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PTER
Introduction to Electricity
• By using an ammeter
• SI unit: ampere (A)– Name after French scientist: Andre-Marie Ampere
• Other units: milliamperes (mA)
1 A = 1000 mA
1 mA = 1/1000 A (or 0.001 A)
Measuring the size of an electric currentMeasuring the size of an electric current
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PTER
Introduction to Electricity
• Connected in series in a circuit• Ammeter has:
- A positive (red) terminal - A negative (black) terminal
• Positive terminal is connected to the positive side of the cell
• Negative terminal is connected to the negative side of the cell
Connecting an ammeter to a circuitConnecting an ammeter to a circuit
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PTER
Introduction to Electricity
• Also called the potential difference• An electric cell provides electrical potential energy, thus
pushing the electrons the circuit.• An electron can have a large amount of potential energy
at one point in the circuit and a low amount of potential energy at another point in the circuit.
• The difference in potential energy between the two points is the voltage.
What is voltageWhat is voltage
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PTER
Introduction to Electricity
• By using a voltmeter• SI unit: volt (V)
- Named after Italian scientist: Alessandro Volta
Measuring voltageMeasuring voltage
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Introduction to Electricity
• In a circuit, electrical components (eg. light bulbs) change some of the electrical energy into other forms of energy.
• The electrons have less potential energy after passing through the component.
• Hence, there is a difference in potential energy or a potential difference.
Why is there a potential difference?Why is there a potential difference?
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E4C
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PTER
Introduction to Electricity
• Connected in parallel in a circuit• Voltmeter has:
- A positive (red) terminal - A negative (black) terminal
• Positive terminal is connected to the positive side of the cell
• Negative terminal is connected to the negative side of the cell
Connecting a voltmeter to a circuitConnecting a voltmeter to a circuit
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Introduction to Electricity
• Different electric sources have different voltages.• Example:
- A 9 V electric cell supplies 6 times the energy of a 1.5 V electric cell
- Mains voltage is much greater.- In Singapore, mains voltage is 230 V.
Voltages of electrical sourcesVoltages of electrical sources
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PTER
Introduction to Electricity
• Different countries use different values of mains voltage to provide electricity to electrical appliances.
• The voltage used range from 100 – 240 V• For example: (Values taken from Wikipedia)
• Find out whether you can still charge your handphone if you travel to countries which use a different mains voltage from Singapore.
Country/City Voltage (V)
Japan 100
Canada 120
Indonesia 127 and 230
Philippines, Hong Kong, South Korea 220
Australia, New Zealand 230
Do you know?Do you know?
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PTER
Introduction to Electricity
• Electric cells are connected in series with the positive terminal of one cell touching the negative terminal of the next cell
• Total voltage across all the electric cells = sum of the voltages of the individual cells
Connecting electrical cells to electrical Connecting electrical cells to electrical appliancesappliances
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E4C
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PTER
Introduction to Electricity
• Electric cells are connected in series with the positive terminal of one cell touching the negative terminal of the next cell
• Total voltage across all the electric cells = sum of the voltages of the individual cells
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PTER
Introduction to Electricity
Complete Theory WB Pg. 34 - 37Complete Theory WB Pg. 34 - 37
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