AC Flashcards
Direct Current
Is a form of current electricity where the polarity of the source does not change.
_____________ are binary circuits which have one of two possibilities.
Logic circuits
Define inductance:
Inductance is the property of electricity that opposes change in current due to a change in the electromagnetic field caused by the current.
Define one time constant, with respect to inductance.
The amount of time it takes for 63.2% of total current to flow in a circuit.
Define capacitance:
Capacitance is energy stored in an electrostatic field.
How is total capacitance found in series? In parallel?
Series: inverse sum of the inverses
Parallel: the sum of the individual capacitors.
Alternating current:
A form of current electricity where the polarity of the source periodically changes.
What are the three common forms of AC?
Square wave, saw tooth wave, sine wave.
Electromagnetic induction:
The creation of an electrical potential in a conductor by passing that conductor through lines of magnetic flux.
On what principle is sine wave produced?
The principle of electro magnetic induction.
What happens in square wave AC?
Polarity periodically changes, but value does not.
What happens in sine wave AC?
Polarity periodically changes, value changes based on sine function.
What happens in saw tooth wave AC?
Polarity periodically changes, value changes with straight line variation.
What two things determine the polarity of the potential produced by electromagnetic induction?
The orientation of the lines of flux
The direction the conductor is cutting the lines of flux
How can the potential produced by electromagnetic induction be increased?
Increase the strength of the flux field being cut
Increase the rate at which the lines of flux are being cut.
What are the advantages of AC over DC?
It is much easier to generate large quantities, it is easier to change values without substantial power loss, and it is much easier to transfer over long distances.
What is a disadvantage of AC?
It is not as efficient as DC.
Alteration:
One half of a cycle, either in the positive or negative direction.
Period:
The time measured for one cycle to occur, measured in seconds.
Frequency:
The number of cycles per second, measured in hertz.
Out of phase:
Any condition other than in phase
Phase shift:
The amount current and voltage are out of range, in degrees of conductor rotation.
Apparent power:
The amount of power that would be dissipated in a d.c. Circuit.
True power:
The amount of actual power dissipated in an AC circuit.
Power factor:
The ratio of true power to apparent power.
Peak to peak value:
The maximum difference between the positive peak and the negative peak value.
How is phase shift measured?
Degrees of conductor rotation?
As current increases the magnetic field _________?
Increases (expands)
As current decreases, the magnetic field ___________.
Decreases, collapses
If current flow reverses, the flux field also ______.
Reverses
Capacitive circuit efficiency?
Least efficient
Resistive circuit efficiency?
Most efficient circuit
Inductive circuit efficiency?
Least efficient
Resonance circuit efficiency?
Most efficient.
How to make a circuit resonant?
Change the amount of inductance in the circuit
Change the amount of capacitance in the circuit
Change the frequency of the circuit
Three phase electricity?
A form of AC which had three separate current and voltage sine waves.
What are the types of three phase windings?
Wye wound, delta wound
