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Chapter 10
Current Electricity
10.1 - Electricity and Electric Circuits
Current Electricity - electric charges flowing in a circuit through a conductor in a
controlled way
The parts of an electric circuit
Energy source
ex: battery
Load
ex: light bulb
Switch
ex: on/off switch
Wires
ex: completes the path and joins everything together
Energy Sources of Circuits
Energy is measured in JOULES (J)
Electrical energy is provided by electrons
Sources of Electrical Energy
Electric cell - converts chemical energy into electrical energy (battery)
Two kinds: Primary Cells and Secondary Cells
Primary cells can’t be recharge; Secondary cells can be recharged
The Load in Circuits
Converts electrical energy into another form of energy.
ex: light from a light bulb; heat from a filament in a toaster; motor in a saw
The Pathway in a Circuit
Conducting wires are used to create a path in a circuit
Copper is the most common conductor (wire) used
Electric Circuit Diagrams and Symbols
Circuit Diagram - represents an electric circuit using standard symbols
Homework: Read 10.1 in your textbook and do the following questions
pg. 305 - # 1 - 12
10.2 - Electric Current
Electric Current (I)- flow of electric charges through a circuit
Like a flowing river
Measured in amperes (A)
Amount of charge through a circuit at a given time.
I (current in amperes); Q (charge in Coulombs); t (time in seconds)
Direction of Electric Current
Flows from positive to negative terminal
Original thought about electricity flow
Known as conventional current
Flows from negative to positive terminal
Modern day electricity flow (because electrons are moving)
Known as electron flow
Direct current (DC)
Electric flow from cells (ex: watch batteries, etc.)
Alternating current (AC)
Electron flow reverses/alternates (electricity in your home)
Series and Parallel Circuits
Series circuits - current goes through each device in sequence
Parallel circuits - current is split up and some of it goes through each device
Measuring Electric Current
Ammeter measures electric current current at a given point in the circuit
Measured in amperes (A) and milliamperes (mA)
Homework: Read 10.2 in your textbook and do the following questions
pg. 309 - # 1 - 15
10.3 - Electrical Potential Difference (Voltage)
Voltage (V)- the change in electric potential energy per coulomb of charge
Measured in volts (V)
Symbol:
Measuring Voltage
Measured using VOLTMETER
Connect voltmeter in PARALLEL to a battery/cell, load, resistor, etc.
Cells in Series
The voltage of cells/batteries in series ADD
ex: 2 - 9V batteries in series gives 18V
Cells in Parallel
Voltages DO NOT add up
ex: 2 - 9V batteries in parallel gives 9V
Homework: Read 10.3 in your textbook and do the following questions
pg. 314 - # 3 - 12
10.4 - Resistors and Ohm’s Law
resistor - resists/opposes the flow of electrical current
Measured in ohms (Ω)
Circuit Symbol:
Resistor code:
Ohm’s Law
The ratio of the voltage across a conductor to the current through the conductor
Can also be written in terms of voltage:
Sample Problems
Sample Problems
Homework: Read 10.4 in your textbook and do the following questions
pg. 319 - # 2 - 7, 10
10.5 - Resistors in Series and Parallel Circuits
Sample Problems
Homework: Read 10.5 in your textbook and do the following questions
pg. 325 - # 2 - 8