Chapter 6: Electricity and Magnetism. Electric Charges Fig 6.3.
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Transcript of Chapter 6: Electricity and Magnetism. Electric Charges Fig 6.3.
Chapter 6: Electricity
and Magnetism
Electric Charges
Fig 6.3
Electrostatic Charge
• Stationary charge confined to an object
• Charging mechanisms– Friction– Contact with a
charged object– Induction
• Stationary charge confined to an object
• Charging mechanisms– Friction– Contact with a
charged object– Induction
Electrical Conductors and Insulators
Measuring Electric Charge
• Unit of charge – Coulomb (C)– Equivalent to charge of 6.24x1018 electrons!– Fundamental metric unit – FYI: Equation 6.1
• Unit of charge – Coulomb (C)– Equivalent to charge of 6.24x1018 electrons!– Fundamental metric unit – FYI: Equation 6.1
Measuring Electrical Forces
Coulomb’s law• Relationship giving force
between two charges• Similar to Newton’s law
of gravitation but…• Ratio of “k” versus “G”
implies gravity weaker.
Coulomb’s law• Relationship giving force
between two charges• Similar to Newton’s law
of gravitation but…• Ratio of “k” versus “G”
implies gravity weaker.2
• Charges surrounded by electric fields • Fields and charges inseparable • Fields act on other charges.
• Charges surrounded by electric fields • Fields and charges inseparable • Fields act on other charges.
Force “Fields”
Electric Potential (V)
Fig 6.8
Equation 6.3
A Volt is a Joule / Coulomb
Electric Current (I)
• Flow of charge• Reason for charge flow:
– Potential differences (voltage)
• Charge per unit time– Thus, a “rate”
• Units?– Coulomb per second [C/s] – Amperes [Amps].
• Flow of charge• Reason for charge flow:
– Potential differences (voltage)
• Charge per unit time– Thus, a “rate”
• Units?– Coulomb per second [C/s] – Amperes [Amps].
The Nature of Current(3 Fundamental Conclusions ; see Fig 6.12 caption)
Fig 6.14Fig 6.12
Electric Circuits
Fig 6.10
DC versus AC
Alternating current (AC)Alternating current (AC)Direct current (DC)Direct current (DC)
How Stuff Works Homepage FSU Homepage
• Charges rapidly change directions
• Household circuits ; Transformers.
• Charges rapidly change directions
• Household circuits ; Transformers.
• Charges move in one direction
• Batteries ; Solar Cells
• Charges move in one direction
• Batteries ; Solar Cells
Electrical Resistance (R)
Electrical Power and Work
Power in circuitsElectric bills
Cost of operating these items?
First: Determine how many Watts (P=IV)Then: First: Determine how many Watts (P=IV)Then:
Household Circuits and Safety
Circuit Breaker
• Three-Pronged Plug• Polarized Plugs• GFCI
• Three-Pronged Plug• Polarized Plugs• GFCI
MagnetismA Property of Electricity
Magnetic Poles and Fields
Fig 6.20Fig 6.19
No matter how you cut it,it keeps coming up a “dipole”
Earth’s Magnetic Field
MagneticDeclinationMagnetic
Declination
Fig 6.21
Fig 6.22
Electric Currents and Magnetism: Current Loops
Fig 6.25
Fig 6.27
Current Loops: Basis of a Solenoid
Note: Magnetic field is like that of a bar magnet.
ElectromagnetsWidely used “device”
GalvanometerFig 6.28
Electric Meters
Fig 6.29
Electric Switches:Relays and Solenoid Switches
ElectromagnetsOther Uses?
Fig 6.30
Telephones and SpeakersElectric Motors
Fig 6.31
Electromagnetic Induction(to induce is to cause)
Fig 6.32
Generators
Fig 6.33
How does “power” get to your house?
Transformers
Fig 6.34
Fig 6.35
Step-down
Step-down
Step-up
Step-up
Next: Exam 2