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    Electricity Electricity Presentation Transcript

    • Atoms…
      • Have neutrons , protons , and electrons .
      • Protons are positively charged
      • Electrons are negatively charged
    • Electrons…
      • Are located on the outer edges of atoms…they can be moved .
      • A concentration of electrons in an atom creates a net negative charge.
      • If electrons are stripped away, the atom becomes positively charged.
    • The world is filled with electrical charges : + - + + + + + + + + + - - - - - - - - -
    • What is this electrical potential called?
      • Static Electricity
      - - - - - - - + + + + +
    • Static Electricity
      • The build up of an electric charge on the surface of an object.
      • The charge builds up but does not flow.
      • Static electricity is potential energy . It does not move. It is stored .
    • Static Discharge…
      • Occurs when there is a loss of static electricity due to three possible things:
          • Friction - rubbing
          • Conduction – direct contact
          • Induction – through an electrical field (not direct contact)
    • Electricity that moves …
      • Current : The flow of electrons from one place to another.
      • Measured in amperes (amps)
      • Kinetic energy
    • How can we control currents?
      • With circuits .
      • Circuit : is a path for the flow of electrons. We use wires .
    • There are 2 types of currents:
      • Direct Current (DC) – Where electrons flow in the same direction in a wire.
    • There are 2 types of currents:
      • Alternating Current (AC) – electrons flow in different directions in a wire
    • simple circuits Here is a simple electric circuit. It has a cell, a lamp and a switch. To make the circuit, these components are connected together with metal connecting wires. cell lamp switch wires
    • simple circuits When the switch is closed, the lamp lights up. This is because there is a continuous path of metal for the electric current to flow around. If there were any breaks in the circuit, the current could not flow.
    • circuit diagram battery switch lamp wires Scientists usually draw electric circuits using symbols;
    • circuit diagrams In circuit diagrams components are represented by the following symbols; battery switch motor ammeter voltmeter resistor
    • types of circuit There are two types of electrical circuits; SERIES CIRCUITS PARALLEL CIRCUITS
    • The components are connected end-to-end, one after the other. They make a simple loop for the current to flow round. SERIES CIRCUITS If one bulb ‘blows’ it breaks the whole circuit and all the bulbs go out.
    • PARALLEL CIRCUITS The current has a choice of routes. The components are connected side by side. If one bulb ‘blows’ there is still be a complete circuit to the other bulb so it stays alight.
    • measuring current Electric current is measured in amps (A) using an ammeter connected in series in the circuit. A
    • measuring current This is how we draw an ammeter in a circuit. SERIES CIRCUIT PARALLEL CIRCUIT A A
      • current is the same
      • at all points in the
      • circuit.
      2A 2A 2A
      • current is shared
      • between the
      • components
      2A 2A 1A 1A
    • Conductors vs. Insulators
      • Conductors – material through which electric current flows easily .
      • Insulators – materials through which electric current cannot move .
    • Examples
      • Conductors :
        • Metal
        • Water
      • Insulators :
        • Styrofoam
        • Rubber
        • Plastic
        • Paper
    • What is Resistance?
      • The opposition to the flow of an electric current, producing heat .
      • The greater the resistance, the less current gets through.
      • Good conductors have low resistance.
      • Measured in ohms.
    • What Influences Resistance?
      • Material of wire – aluminum and copper have low resistance
      • Thickness – the thicker the wire the lower the resistance
      • Length – shorter wire has lower resistance
      • Temperature – lower temperature has lower resistance
    • What is Voltage?
      • The measure of energy given to the charge flowing in a circuit.
      • The greater the voltage, the greater the force or “pressure” that drives the charge through the circuit.
    • Difference between Volts and Amps
      • Example – you could say that…
        • Amps measure how much water comes out of a hose.
        • Volts measure how hard the water comes out of a hose.
    • Ohm’s Law Ohm's Law defines the relationships between (P) power, (E) voltage, (I) current, and (R) resistance.
      • Resistance = Voltage / Current
      • Ohms = Volts / Amps
    • Practice with Ohm’s Law 8 48 6 5 45 9 15 30 2 10 150 15 25 100 4 Amps Volts Ohms