Electricity and magnetism (unit 5 and 6) Flashcards
Charge = ?
units
Charge = current * time
Q = I * t
Q = C (coulombs) I = A (current) t = S (seconds)
Ferrous materials?
4
Attracted by a magnet and can be magnetised
Iron
Nickel
Steel
Cobalt
Steel = Permanent Iron = Temporary
Non - ferrous metals
5
Not attracted by magnet and can’t be magnetised
Copper Silver Aluminium Wood Glass
Electrical field intensity
+ Equation
Amount of force exerted by the charge on a unit charge (Q) placed at a point in the field
E = F / Q
Ohms law
+ Equation
Voltage across resistor is directly proportional to current
R = V / I
R (measured in Ohms)
P.d (potential difference) - Voltage
V = Energy / Charge
V = E / Q
E.M.F (electromotive force)
EMF = lost volts inside the power source + terminal p.d
EMF = Ir + IR
Resistance and resentivity
R = resentivity * (Length of a resistor / Area of cross section of the resistor)
R = resentivity * (L / A)
Current:
- Series
- Parallel
- Series = Stays the same
- Parallel = Current divides
Voltage:
- Series
- Voltage
- Series = Divides
- Parallel = Stays the same
Total Resistance in series
R = R1 + R2 + R3
The R’s are all resistances of resistors in Ohms
Total Resistance in parallel
1 / R = 1 / R1 + 1 / R2 + 1 / R3
Potential divider or potentiometer
V1 / V2 = R1 / R2
Potential divider
V2 = (R2 / (R1 + R2)) * V
Power
4
- P = V * I
- P = I^2 * R
- P = V^2 / R
- P = Energy / time
Diode function
Semiconductor device
Current pass only in one direction, rectifier
Transistor function
Semiconductor device works as a switch, collector, base, emitter
Light dependent resistor function
LED
LED is dependent on light
Brightness increase = resistance decrease
Thermister function
Dependent on temperature
Temp increase = resistance decrease
Capacitor function
Parallel conductor with insulator in between to store changes
Relay function
Electromagnetic switching device
Fleming’s left hand rule
Thumb = Motion
First finger (index) = Field
Second finger = Current
Transformer equation
voltage
Np / Ns = Vp / Vs
Transformer equation
(Current)
(2)
Vp / Vs = Ip / Is
Vp * Ip = Vs * Is
E.M induction
EMF or current is induced in a conductor when it cuts the magnetic field lines
A.C generator
Produces current
Fleming’s RIGHT hand rule
D.C generator
Consumes current
Fleming’s LEFT hand rule
Name the 5 common logic gates and how they work
- AND (both input needs to be 1 for output to be 1)
- OR (output will be 1 if one or both inputs is 1)
- NOT (opposite of the input)
- NAND (output is 1 when input = either 1/0 0/1 0/0)
- NOR (output will be 1 when input = 0/0)
Cathode rays
Stream of electrons emitted from heated metal (cathode)
Process is called thermionic emission
CRO
Horizontal or y-plates for vertical movement of electron beam
Timebase for x-plates for horizontal movement
