P6

P6

1. transistors

   • base- if a small current is flowing through the base then a larger current can flow through the collector then out of the emitter
   • a transistors is a switch effectively
     • a current passing through the base will pass into the emitter, if its large enough then the collector is activated... IE = IB + IC
   • two transistors combined can make an AND gate, a small current from input A and input B will only then allow the current from the top collector to flow through to the bottom
     • resistors are placed in the circuit to maintain the low current

2. logic gates

   • logic gates need a signal to work, the signal is either described as 1 (high/ 5v) or 0 (low/0v)
   • types of gates
     • NOT gates: The input is the opposite of the output
       • AND gates: The output is only active when both inputs are active (high)
         • OR gates: The output is only active when one or both inputs are active
           • NOR gates: this is a NOT gate plus an OR gate. So a high current passes from the output only when there is a low signal from either input. if either or both outputs are high then no current passes through.
             • NAND gates: a high current passes through the gate in all combinations except when there is a high signal in both inputs
           • effectively like: two switches in parallel
   • Truth tables are used to show what combination is needed for a certain output

3. motors

   • The commutator
     • The Commutator allows the motor to keep spinning, without it the coil will just turn till is vertical
     • Most practical motors have curved magnets so as he coil spins its always at right angle to the field
     • The force of the field and coil allow it to spin but at vertical the inertia/momentum from the preceeding spin makes it go o the other coil to spin
     • The split ring aciton of the commutator means hathere is no current passed through the coil while vertical. There is a DC current sent from the batery. the split ring means that current in the wire is always alternating
     • https://www.youtube.com/watch?v=Jg4BkhyNbRg
   • IN a wire where current flows there is a magnetic field surrounding it. (Right hand grip rule) ^
     • When the wire is in a magnetic field the fields interact causing movement
       • When a current is placed through a coil betweens the poles of a magnet, there is a force on each side of the coil. The left hand rule shows that forces are in opposite directions. One side is forced up as the other is forced down. this causes the motor to spin
         • Motor turns faster: - No of coil turns, -Size of the current. -Strength of the wire
   • A Bar magnet and coil share the same type of field its called a solenoid
     • the left hand rule is used to determine the movement of the with wire

4. diodes

   • LEDs Light emitting diodes
     • Relays: relays are made from a common (COM), A Normally closed, and a Normally Open
       • a relay is

5. generators

   • When a magnetic field is moved through a wire a current is induced.
   • AC
     • supply electriciy at 50hz
   • DC (Dynamo)
   • Electricity useful as can be easily transferred using the national grid. Can be stored in hydro-electric facilitys
   • Induced voltage
     • Reversing the direction of a magnetic field, also reverses the induced voltage and current direction.
     • Voltage is induced whenever a magnetic field changes
       • When a magnetic field inside a coil changes. a voltage is induced across the coil and a current passes through the coil

6. transformers

7. non ohmic/ohmic conductors

8. potential dividers

9. LDRs and thermistors

   • light dependent resistors
     • LDR's are resistors that only work in certain conditions of light, an LDR only allows current to flow (low resistance) when there is a high amount of light
   • Thermal resistor: the resistance of a thermal resistor decreases as the the temperature increases.

10. capacitors

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