Current-and-Voltage (1)
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Title: Current and Voltage
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Importance of Electricity Education
From Grade 3 to Grade 7, students have learned the following about electricity:
Sources and uses of electricity.
Conductors of electricity.
Components of an electric circuit.
Energy transfer in electrical systems.
Key Quantities in Electricity:
Current.
Voltage.
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Definition of Electricity:
Electricity: A form of energy that can easily be converted to other forms.
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Sources of Electricity:
Power Stations
Provide large amounts of electricity.
Used for many electrical appliances.
Electric Cells (Batteries)
Provide smaller amounts of electricity.
Portable and safe to use.
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Functioning of Electrical Appliances:
Electricity needs to flow through an appliance to operate.
The flow of electricity is defined as electric current.
The path for electric current is called an electric circuit.
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Important Concepts in Electricity:
Electrical Power
Electrical Energy
Electric Circuit/Connection
Ohm’s Law
Electric Charge
Electric Force
Electric Field
Electric Potential
Electric Current (I)
Electrostatics
Magnetic Field and Current
Electrical Connections at Home
Progression from Grade 7 to Grade 8 topics.
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Additional Topics on Electricity:
Magnetic Field (B)
Magnetism
Electromagnets
Motors
Faraday’s Law
Generator/Transformer
Power Transmission
Interaction of magnetic fields and current.
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Investigation:
Explore the relationship between current and voltage.
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Learning Goals:
Define current and voltage.
Determine current and voltage in circuits.
Explain the relationship between current and voltage.
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Components of Electric Circuits:
Made up of electrical components:
Connecting wires.
Electric cell.
Light bulb.
Circuit board.
These components must form a closed circuit with no gaps.
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Understanding Open Circuits:
An incomplete circuit is an open circuit.
Caused by missing connecting wire or lack of electrical energy source.
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Components Required for Electric Current:
Source of Electrical Energy
Connecting Wire
Load
Switch
Must form a CLOSED circuit.
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Simple Electric Circuit Definition:
Arrangement allowing electrons to flow, containing:
Source of electric energy.
Parts converting electric energy into other forms.
Questions about electrical circuit components and functionalities.
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Circuit Example with a Bulb and Power Source:
Discuss who answered correctly regarding circuit functionality.
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Activity: Current and Voltage:
Define current and voltage using circuit illustrations.
Voltage ratings of dry cells and bulbs.
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Definition of Electric Current:
Electric current: The rate of flow of electric charges in a circuit.
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Composition of Electric Charges:
Made of positive (protons) and negative (electrons) charges.
Flow in a circuit produces current.
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Mechanism of Electricity Flow:
Battery energizes electrons, pushing them from the negative to the positive terminal around the circuit.
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Measurement of Electric Current:
SI unit is Ampere (A).
Smaller current in Milliamperes (mA); conversions:
1 A = 1,000 mA
1 mA = 0.001 A
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Contribution of Andre-Marie Ampere:
Founder of Electromagnetism.
Birth: January 20, 1775; Death: June 10, 1836.
His legacy includes the SI unit for electric current: the ampere.
Notable achievements and contributions to science.
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Summary of Electric Current:
Defined as a measure of electric charge flow in a circuit:
Formula: current = charge/time (I = q/t)
Charge of an electron: 1.6 x 10^-19 coulomb.
1 coulomb = 6.3 x 10^18 electrons.
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Types of Electric Current:
Direct Current (DC): Flows in one direction (e.g., batteries, flashlight cells).
Alternating Current (AC): Periodically reverses direction (e.g., household current).
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Ammeter Definition:
Instrument used to measure electric current.
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Ammeter Connection:
Must be connected in series within the circuit.
Positive terminal should connect to the positive side of the battery.
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Understanding Voltage:
Voltage provides energy to electrons, facilitating their movement in a circuit.
Different voltage ratings from different cells/batteries.
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Definition of Voltage:
Voltage (or potential difference): Work done or energy transferred between points in a circuit per coulomb of charge.
Measurement in volts (V): 1 V = 1 J/C.
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Measurement of Voltage:
SI unit for voltage is Volt (V).
Voltmeter: Instrument used for measuring voltage.
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Alessandro Volta's Contributions:
Invented the electric battery.
Established the unit of electric potential named after him.
Other noteworthy achievements in science.
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Voltmeter Connection:
Must be connected in parallel to the circuit for accurate measurements.
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Questions Regarding Circuit Behavior:
Brightness of bulbs in different circuits & cause of bulb illumination.
Evaluation of electric charge behavior.
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Understanding Resistance:
Resistance opposes electric current flow:
Low resistance implies good conductors (e.g., metal).
High resistance implies poor conductors (e.g., wood, cloth).
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Usage of Materials in Appliances:
Copper wire for external wiring due to low resistance.
Nichrome wire for heating elements due to high resistance.
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Ohm’s Law Overview:
Formula linking voltage, current, and resistance:
Ohm’s Law Formula: R = V/I
Alternate forms: V = I x R; I = V/R
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Calculation Example:
IF a bulb has a current of 20 A and a voltage of 100 V:
Resistance Formula: R = V/I = 100V/20A = 5 Ω.