Chapter 17: Introduction to Electricity

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# Chapter 17: Introduction to Electricity - PowerPoint PPT Presentation

Chapter 17: Introduction to Electricity. Review. 1. Definitions:. law of electric charges (like charges repel and opposite charges attract) electric force (the force between charged objects), electric field (space surrounding electrically charged particles),

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Presentation Transcript

1. Definitions:

• law of electric charges (like charges repel and opposite charges attract)
• electric force (the force between charged objects),
• electric field (space surrounding electrically charged particles),
• electrical conductor (a substance in which charges can roam),
• electrical insulator (a substance in which charges do not roam),
• static electricity (an electric charge at rest on an object),
• electric discharge (the loss of static electricity as charges run off of an object),
• electric current (the rate at which charges pass through a specified point),
Definitions

i) voltage (potential difference between two points in a circuit),

j) resistance (the opposition to the flow of electric charge),

k) electric power (the rate at which electrical energy is converted into other forms of energy),

l) series circuits (all parts are connected in a single loop),

m) parallel circuits (loads are connected-side-by side).

2. The three ways of charging an object
• Conduction:

electrons move between objects by direct contact

• Induction:

rearrangement of charges in an uncharged object without direct contact

• Friction

transfer of charge through rubbing/wiping

3. Electrical insulator and conductors
• Examples of insulators:

plastic, rubber, glass, wood, etc.

• Examples of conductors:

copper, aluminum, mercury, etc.

4. AC and DC current
• AC current:

charges continually change direction

Applications: houses (AC changes direction 120 times a second)

• DC current:

charges flow in the same direction.

Applications: batteries

5. The relationship between voltage, resistance and current

• If voltage increases, current also increases
• Resistance increases as current goes down (voltage must be constant)
6. Resistance, thickness, length, and temperature
• Resistance decreases with thickness
• Resistance increases with length
• Resistance increases with an increase in temperature (virtually at low temperature there is no resistance) e.g. superconductors
7. Equations

Ohm’s law: V = I * R

electrical power: P = V * I

electrical energy (E = P * t)

17.3: Ohm’s Law
• Current is proportional to voltage
10. Components of an electrical circuit

1. energy source

2. wire