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
