RLC Flashcards
Inductance opposes a change in _____
Current
Inductance of a coil is not effected by the _____
Frequency of applied voltage
To find inductive reactance of a circuit you must know _____ and ______
Frequency and inductance
There is no phase difference between current and voltage across ____
A. Inductor
B. Resistor
Resistor
Capacitance opposes the change in _____
Voltage
In series RC, the voltage across the resistor is in phase with the current, true or false?
True
If a series is resonant, circuit impedance is equal to _____
Circuit resistance
Capacitors in parallel add _____
Directly.
C1 + C2 + C3
Capacitors in series add _____
Inversely
When a circuit is pure resistance the PF is _____
1
In a parallel resonant circuit the impedance is at a _____ and line current is at a _____
Maximum, minimum
In a series resonant circuit the impedance is at a _____
Minimum
When frequency of an inductive circuit increases, the current ______
Decreases
In AC capacitance, the current varies directly with the _____
Frequency
XL =
2pi • f • L
L=
XL / 2pi • f
Q factor =
XL / R
R = Esquared / P
Transpose
P = E squared / R
P = I squared / R
Fr =
1 / 2pi • square root LC
When comparing DC and AC circuits, the DC value will always be what part of the vector?
X axis (resistance)
When comparing DC and AC circuits, AC values will always be on what part of the vector?
Hypotenuse
Two principal parts of a capacitor
Plates, dielectric
Two principal parts of an inductor
Coil, core
There is no inductance in a DC inductive circuit after five time constants. T/F?
True.
What is the danger of putting an inductor in a DC circuit?
The current can be dangerously high
What side of impedence triangle is impedance?
Hypotenuse
What side of impedance triangle is reactance?
Opposite
What side of impedance triangle is resistance?
Adjacent (x axis)
Henries add ______ in series
Directly
Henries add _______ in parallel
Inversely
Capacitors add _______ in series
Inversely
Capacitors add ________ in parallel
Directly
In induction any change in current means change in flux. T/F?
True
Inductance is the property of a circuit that opposes any change in current in that circuit. What does this mean for current?
If current increases, induced EMF will try to push it back down. If current decreases induced EMF will try to push it back up.
Induced voltage opposes applied voltage. T/F?
True.
A voltage is induced across the conductor when ______
The magnetic field collapses
How do you prevent a dangerous arc at a switch when opening a DC inductor?
Free wheeling diode or field discharge resistor
How does a free wheeling diode work?
Before a free wheeling diode is installed when the switch is opened the inductor will try to maintain current slow causing an arc across the switch. When the FwD is added into the circuit the inductor acts as a source, the polarity of the FWD changes and now current will flow through the diode until all energy is dissipated instead of arching.
How to calculate current after ___seconds.
I = t • E/L
Ex) I = 10s • 20V/10H = 20A
What is the main effect of an inductor in a DC circuit?
To slow rate of current rise.
What is the formula for tau?
L/R
Capacitors oppose a change in ______
Voltage
What will happen to current of a capacitor when source is changed from AC to DC?
It will decrease. DC does not change polarities so the capacitor cannot discharge
What happens to XL when turns increase?
Increases
How many decimal places to move for micro farads
6
In non resonance and resonance do the watts of the resistor change?
Yes
Formula for L
XL / 2pif
Write this down
When converting an equation to resonance, which value do you keep?
Frequency, resistor resistance
When frequency is increased, inductance _______ and capacitance _______
Increases, decreases
When resistance and inductance is on the same angle, the PF is
100%
When calculating motor input and output, what is the process of calculating the three values by pf and ef?
hp x 746 gets output, divide output by efficiency, that value is watts. Divide watts by power factor, that value is input.
Where do you put the value of watts from the motor?
Watts calculated from the motor goes on watts of the resistor of the motor when broken down between resistor and inductor.
Where do you put the value of input when calculating motor?
Input value is the VA of the motor WIRE
Where do you find the VaR of the inductor on the motor wire?
Input squared minus watts squared
When looking at a sine wave, what do the block lines represent?
1 alternation
How many degrees is 1 alternation?
180
How do you calculate the angle of a sine wave?
Find amount of blocks in 1 alternation.
180/# of blocks = degree of each block. Count blocks between different sine waves and multiple degrees by that amount.
