Unit 2: Electricity

  • Created by: tdicks
  • Created on: 24-11-18 15:11
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  • Electrons
    • Power
    • Voltage
    • Resistance
      • in parallel
        • resistance is less than the smallest resistance value
          • because a larger amount of electrons flow through the circuit
      • in series
        • R = r1+r2+r3
          • because electrons make more collisions
      • depends on ...
        • length of wire
          • REQUIRED PRACTICAL
        • light intensity
        • temperature
        • I/V graphs
          • wire resistor
            • DIAGONAL
              • as V increases
                • resistance is constant
                  • resistance = 1/gradient
                • Untitled
                • resistance increases
                  • because temperature of filament increases
                    • electrons collide more and vibrate with positive ions
                • V is directly proportional to I
                  • ohmic conductor
                • Untitled
                • Untitled
          • filament lamp
            • S SHAPE
              • as V increases
                • resistance is constant
                  • resistance = 1/gradient
                • Untitled
                • resistance increases
                  • because temperature of filament increases
                    • electrons collide more and vibrate with positive ions
                • V is directly proportional to I
                  • ohmic conductor
                • Untitled
                • Untitled
          • LED
            • LINE, UP
            • required practical
        • R = V/I
          • V = voltage
            • measured in volts
          • I = current
            • measured in amps
          • R = resistance
            • measured in ohms
      • Current
        • ammeter connected in series
          • resistance very small
            • doesnt reduce current
        • always the same current
          • because charge is reserved
        • current leaving cell is current entering cell
          • because charge is reserved
        • sum of current in parallel are branches added up
          • I = Q/t
            • I = current
              • measured in amps
            • Q = Charge
              • measured in coulombs
            • t = time
              • measured in seconds
          • electron flow is ac
            • 230 mains voltage
              • provided by power station
                • step up transformer connected
                  • reduces current in overhead cables
                    • step down transformer connected
                      • reduces voltage
                  • step down transformer connected
                    • reduces voltage
                  • increases voltage
              • 3 pin plug
                • case
                  • plastic
                    • insulator
                • wires
                  • copper
                    • conductor
                • earth wire
                  • green and yellow stripes
                    • 0 volts
                      • carrries current if there's a fault
                        • prevents appliance becoming live
                • neutral wire
                  • blue
                    • 0 volts
                      • carries current back to source
                        • prevents user getting an electric shock
                • live wire
                  • brown
                    • 230 volts
                      • contains a switch
                        • very dangerous
                • contains
                  • 2 cores
                    • live and neutral
                  • 3 cores
                    • live, neutral and earth
            • flow reverses 50 times per second
              • 50 Hz
          • electron flow in one direction is direct current
            • provided be cells and batteries
              • contain chemical energy stores
        • Electrostatic Charge
          • when you gain electrons, you gain negative isulator charge
            • eg. brushed hair stands on end
            • when you loose electrons, you gain positive insulator charge
              • Electrostatic Charge
                • when you gain electrons, you gain negative isulator charge
                  • eg. brushed hair stands on end
                  • when you loose electrons, you gain positive insulator charge
                    • eg. brushed hair is attracted to brush
                • force at a distance is a non-contact force
                  • force is experienced at an electric field
                    • point charge is radial
                      • ARROWS OUTWARDS
                        • repulsive charge on a positive charge
                        • force decreases as distance from charge increases
                      • arrows show direction of force on a positive charge
                        • ARROWS OUTWARDS
                          • repulsive charge on a positive charge
                          • force decreases as distance from charge increases
                        • ARROWS INWARDS
                          • attractive charge on a positive charge
                      • ARROWS INWARDS
                        • attractive charge on a positive charge
                    • causes sparking between charged object and earth
                      • when force on air icles is large enough to ionise air
                        • so electrons are transferred between charged object and earth
              • eg. brushed hair is attracted to brush
          • force at a distance is a non-contact force
            • force is experienced at an electric field
              • point charge is radial
                • arrows show direction of force on a positive charge
                • causes sparking between charged object and earth
                  • when force on air icles is large enough to ionise air
                    • so electrons are transferred between charged object and earth

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