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Electricity - PowerPoint PPT Presentation

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Electricity. The flow of charges. Atoms. Made up of: Nucleus: Protons and neutrons Electrons: negative charge orbit nucleus. Current. Flow of electrons Measured in Amperes (Amps) Electrons passing per second. Circuit. Must have complete, unbroken path for current to flow 3 Parts:

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Presentation Transcript


The flow of charges


  • Made up of:

    • Nucleus: Protons and neutrons

    • Electrons: negative charge orbit nucleus


  • Flow of electrons

    • Measured in Amperes (Amps)

      • Electrons passing per second


  • Must have complete, unbroken path for current to flow

    • 3 Parts:

      • Load: device run by electricity

      • Wires: path for electron flow

      • Source: moves the electrons through the wire

        • Battery, generator, wall socket (power plant)


  • Materials allowing electrons to flow

    • Examples:

      • metals: electrons loosely held, move easily

        • Copper is one of the best


  • Do not allow electricity to flow

    • Examples: rubber, plastic

      • Electrons held tightly, will not move easily


  • Measures the force “pushing” electrons

    • Volt (v) as unit

      • Higher voltage is higher potential to push electrons through circuit


Lower Potential energy =Low voltage

Higher Potential energy=high voltage


  • Force working against (“resisting”) the flow of electrons

    • Measured in Ohms (Ω)

    • All parts of circuit “slows the flow”

Ohm s law


I =


Ohm’s Law

  • Tells how current, voltage, resistance are related

    • Current = voltage


Practice ohm s law
Practice Ohm’s Law

  • A 9 volt battery is used to light 3 bulbs with a resistance of 0.5 Ω each. Wires and a switch add another 3 ohms of resistance. How much current (amps) is flowing through the circuit?

    • Plan

      • What information is given?

      • 9 volts, 3 bulbs x 0.5 ohms = 1.5 ohms plus 3 ohms for total of 4.5 ohms.

    • What formula do I use?

      • I = v / r

      • I = 9 v / 4.5 Ω

    • Solve

      • I = 2 amps

    • Check:Does it make sense?

      • The current is less than the voltage because the resistance is reducing the flow

Series circuit
Series Circuit

  • Only one path for electricity to flow

    • What happens if one bulb goes out?

    • Will the bulbs be dimmer or brighter than a parallel?

Load (bulb)


Parallel circuit
Parallel circuit

  • More than one path for electricity to flow

    • Each load on separate circuit

    • What happens if one bulb goes out?

  • Compare series/parallel to water supply

Current direction
Current Direction

  • Current always flows in one direction:

    From negative to positive

AC vs. DC

Direct current dc
Direct CurrentDC

  • Charges always flow in same direction, from negative terminal to positive terminal

    • Battery (cells)

Cells and batteries

anode collector

plastic seal

plastic sleeve


steel jacket

Case sleeve

Cell straps


Negative terminal

cathode collector


Positive terminal

Cells and Batteries

9 Volt Battery

  • Convert chemical energy to electrical energy

    • Potato clock

Electron acceptor

Electron donor

Other sources of dc
Other sources of DC

  • Thermocouple: convert heat to electricity

  • Solar cells: convert solar energy to electricity

Alternating current ac
Alternating CurrentAC

  • Charges flow from negative to positive but switch directions back and forth (alternate)

    • House current

Producing ac current
Producing AC current

  • Induction: Coil of wire and magnet produce electricity

  • It’s electro-magnetism!

    • Generator: converts mechanical energy to electrical energy

    • Motor: converts electrical energy to mechanical energy


  • Magnetism and Electricity are closely related

  • Electric current causes magnetic fields

    • Cell phones, television, light

  • Magnets can cause an electric current to flow

    • Generators


  • Measures how fast energy is transferred from one form to another

  • Measured in Watts

    • Power = voltage x current

      • P= V I

      • A 100 watt light bulb changes or uses electrical energy to light energy twice as fast as a 50 watt bulb

  • Brainpop on current