P6 | Mindmap

Definitions
1. Voltage (potential difference): work it takes to move charge from one part of the circuit to the other (V)
2. Resistance: measure of how hard it is for current to flow (Ohms)
3. Current: rate of flow of an electric charge (A)
Equations
1. Resistance= voltage/current
Logic gates
1. AND: A & B need to be on
2. NOR: when A & B are off out put is on, when A or B or both are on, output is off
3. NAND: out put is always on except when A & B are on
4. NOT: is the reverse of what it was
5. OR: A or B or both
Resistance
1. L.D.R: Light dependent resistor. bright light= less resistance dim light= more resistance
  1. street lamps
2. Variable resistors can change resistance, it is altered by the length of wire
3. Ohmic conductors follow Ohm's law, resistance- voltage/current. the resistance stays the same
  1. copper
4. non-ohmic conductors don't follow Ohm's law, the resistance varies
  1. light bulbs
5. thermistor: high temperature=less resistance low temperature=more resistance
  1. incubator
6. Thick wire has less resistance as there is a bigger area for electrons to flow
transistors
1. Emitter=Base+Collector
2. Current flowing into the base has to be of a certain value, once it is current is allowed to flow into the collector and out the emitter
3. they act like switches and amplifiers
4. the current passing through the collector and emitter is bigger than at the base, therefore it acts like an emitter
magnetic currnet
1. right hand grip method
2. left hand rule
3. motors: turns electrical energy into kenetic
  1. split ring commutators change charge every half turn keeping the motor spining
  2. increase speed of motor: bigger current, more turns of wire, stronger magnet
4. electromagnetic induction
  1. when a wire is passed through a magnetic field and cuts the field lines creating current
  2. when wire moves in the direction of field lines no current is produced as field lines aren't cut
5. Generators, kenetic energy into electrical
  1. magnetic field moves rather than coil of wire
6. Transformers, only work with A.C
  1. step up
    1. increase voltage
    2. have more turns on the secondary coil
  2. step down
    1. decrease voltage
    2. have fewer turns of the secondary coil, used in everyday applications
  3. isolating transformers
    1. same number of coils on each turn
rectification
1. half wave rectification
2. full wave rectification
3. with a capacitor
4. diode, allows current to flow in one direction
  1. P & N, electrons travel from positive to ngative
    1. N has extra electrons
    2. P has missing electrons "holes"
    3. "holes" move from positive to negative
  2. forward bias
    1. narrows depletion layer which decreases resistance
  3. backward bias
    1. widens depletion layer which increases resistance
5. capacitor
  1. stores electrical charge form a battery then discharges it later
  2. have two plates, positive and negative
  3. can be used with four diodes, diodes make sure current is direct, capacitor smooths output

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P6

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