Theory Induc And Cap Flashcards
What is inductance
Inductance is the property of a circuit that opposes change in current
What is induction
The process where voltage is produced by the relative motion between a conductor and a magnetic field
What is an inductor
An electrical component that stores energy in its magnetic field
What affects the amount of emf generated
Density of flux
Length of conductor in mag field
Rate and angle which conductor cuts lines of force
One cycle is how many alternations
2 one positive one negative
Frequncy is determined by
Electrical cycles per second
North america runs on what frequency
60 hz
To find e max you blank e rms or e ins by sin 45
Divide
To find e rms you blank emax by sin45
Multiply
To find instantaneous values you blank emax by the sin of the angle your looking for
Multiply
What value does a meter show
RMS value or root means square
What is the effective value of a voltage sinewave
Value of an ac voltage that produces heat in a cct at the same rate as a dc cct
Where does an inductor store energy
An electromagnetic field
Other than a coil what are 2 common names for an inductor
Solenoid or reactor
A transformer is an inductor true or false
True
Examples of electrical equip that use coils
Transformers
Motors
Solenoids
Relay coils
Magnetic starter coils
Lighting ballasts
Line reactors for vfd
What is induction
The process of producing ciltage through relative motion between a field of flux and a conductor
What is faradays law
Amount of induced emf is directly proportional to rate of change of flux
2 types of induction
Mutual and self
What is lenz law
The polarity of any induced voltage must create a flux that opposes the current it creates
What affects cemf in a coil
Inductance and rate of change of current
Define inductance
Property of a cct that opposes a change in current
What is the unit of meausurment for inductance
Henrys
Capacitors are polarized or not
Both normally not
Six types of non polarised capacitors
Air
Oil
Paper or tubular
Plastic film
Mica
Ceramic
What capacitor type is easily adjusted
Air
What are oil capacitors good for
High current and voltage
What is a benefit to ceramic capacitors
Large capacitance for their size
Are electrolytic capacitors polarised or non
Both
4 uses for capacitoors
Timers
Rectifier smoothing and filtering
Power factor correction
Motor starting
Define capacitance
A capacitors ability to hold an electric charge
Capacitance is measured in what
Farads
What 3 factors affect capacitance
Dielectric consgant of material between plates(k)
Area of the plates (A)
Distance between the plates (d)
What is a dielectric constant
Ability for a material to store and hold charge compared to air
What is dielectric strength
The max voltage that a dielectric can withstand before it begins to breakdown
Wvdc stands for what
Working volts dc
How to calculate max ac voltage from wvdc
Vrms=vmax x sin 45
What is a time constant and how many does it take to get to steady value
Time it takes a cct value to change by 63.2%
5
In inductance what starts at a steady value and what starts at a minimum value
Current minimum
Voltage maximum
What is a discharge resistor
A resitor wired in parralell that is used to disperse induced voltage or inductive kick across a switch
Coulumb is the unit of measurment for what
Electric charge
In a capacative circuit what starts at steady calue and what starts at minimum
Voltage minimum
Current steady state
What is inductive reactance
Opposition to current flow in a ac cct
Does inductive reactance happen in dc
No
What is capacative reactance
Force that limits total current in an ac cct
