Electricity Flashcards
2 Semi Conductors
Silicon, Germanium
Difference between EMF and Terminal Voltage
EMF: Force that converts energy into electricity.
PD: Amount of energy transferred between two points in a circuit
What is capacitance measured in?
Farad
What is the unit of Inductance?
Henry
Low Pass RC Filter
Voltage divider that filters out higher frequency signals
High Pass RC Filter
Voltage divider to remove lower frequencies
Barrier potential of Silicon
0.6V
Barrier potential of Germanium
0.2V
EM Induction Principle
An EMF or PD is induced when a conductor moves through a magnetic field or a changing magnetic field cuts through a stationary conductor
Faradays Law
the magnitude of the induced EMF is proportional to the rate of change of the magnetic field.
Lenz Law
It states that the direction of the induced current in the coil will be always in such a way that it opposes the change which produces the current.
Copper Loss
Loss of conductivity in transformer windings due to resistance of the copper.
Eddy Currents
loops of electrical current that are created in a conductor when there is a change in the magnetic field, or when the conductor moves through a magnetic field.
What does a laminated core do to the eddy current
Reduces the lass due to eddy currents dramatically.
2 roles of a diode
Ensures current only flows in one direction.
Turns AC into DC (rectification)
How do we reduce the output ripple in a diode bridge
Add capacitor in parallel with load
4 conditions for a generator to be connected in parallel
Frequency of all generators is the same.
Voltages of the generator are equal.
Phase sequence must be the same.
They must be In-Phase.
How is initial excitation achieved in brushless generators
A permanent magnet field excites the alternator as it rotates.
How do we correct an imbalance in reactive power (kVAR)
Increase or decrease the torque
How do we correct an imbalance of real power?
Increase or decrease the field current
What are the conditions required for self excitation of a shunt connected to a DC generator?
There must be enough Residual Magnetism (flux) in the field poles.
How do we rectify output?
Commutators and or diode bridge
