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Electrical Charge & Current

Unit 5: Electricity

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Electricity

Electricity is a force created by a difference in charges (+ and -) due to gained or lost electrons

  • Electrons are negatively charged particles

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Electrical Current

When electricity is flowing between two points, the electrons are actually moving from Point A to Point B

  • This movement is called an electrical current

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Electrical Flow

For the electrons to flow, there must be a difference in charges between the two points

  • Electricity always flows from areas of negative charge to areas of positive charge

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Voltage & current

Voltage is the difference in charges between two points

The number of electrons actually flowing through a conductor is called the current

    • Current is measured in amperes (amps)
    • 1 amp = 6.25 x 1018 electrons per second
      • That’s 6,250,000,000,000,000,000

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Voltage & current (Not in your notes)

Two points can have a tremendous charge, but if the charges are the same then there will be no flow of electrons between the two points

Using a voltmeter, you determine that there are no electrons flowing from Point A to Point B through an extension cord. Does that mean it is safe for you to touch either of the two points?

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Voltage & current (Not in your notes)

NO! There may not be electrons flowing because the charges are the same between the two points, BUT the charge you carry might be different which would allow the electricity to flow into you

  • Long story short: you would be electrocuted

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Resistors

Resistors are materials that can slow the flow of electricity without stopping the flow all together

    • Almost all materials provide a small amount of resistance to an electrical current
    • Resistance is measured in ohms (Ω)

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Conductors & Insulators

A conductor is any material through which electricity (energy) flows easily

  • Examples: metals, water

An insulator is any material which prevents the flow of electricity (energy)

  • Examples: rubber, glass, wood, plastic

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Types of Electrical Currents

Two types:

  1. Direct current (DC)
  2. Alternating current (AC)

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Direct Currents (DC)

In most electrical circuits, the current will only flow in one direction

  • This type of circuit is called a direct current (DC)

Examples of direct currents are:

    • Batteries
    • Lightning
    • Static electricity

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Alternating Currents (AC)

In alternating currents (AC)the direction of the flow of electrons switches back and forth at regular intervals or cycles

  • Most household AC circuits reverse the direction of the current 120 times per second

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DC vs AC

Direct Current

Alternating Current