test #3!!! Flashcards
What are the three primary types of loads in AC circuit
Resistive load inductive load capacitive load
Can you give an example of resistive load
Incandescent bulb electric heater any electrical load that consists of only heating elements
Can you give an example of inductive load
Electric motor that are used in various appliances such as washing machines refrigerators and air conditioning
Can you give an example of capacitive load
A battery in charging condition a motor starter circuit
What is the basic law of induction
Whenever current flows through a conductor a magnetic field is created around the conductor
Where L inductance N = number of turns of a wire the strange U equals permeability of a core material a equals cross-section area of the core material and I equals the length of a core please write down the formula for calculating the inductance of a coil
L = μN2A/l
what is the unit of measurement for inductance please include both the name and the letter symbol
L inductance measured in Henry’s symbol H
How much induced voltage will occur when a coil has one Henry of inductance and a current change of one amp per second
One voltage
The time necessary for current in an inductor to reach its full ohms law value is called what
Time constant
What is the formula for computing the time of one time constant
C=t/R
An inductor has an inductance of 0.25 Henry’s and a resistance of five ohms how will it take to reach its full ohms law value
.25 sec
Why is there always some amount of inductance in an A C circuit
Because of the continually charging magnetic field
For the most part we do not take into consideration the inductance in branch circuits or in single conductors a C circuit in circuit calculation why is that this
Because the inductance is very small
What type of a C circuit do you consider inductance in their calculation
When any type of load contains a coil being used
What is the letter used to represent inductance in an A C circuit
L
CEMF Is the result of an induced voltage being opposite in polarity to the applied voltage what does it stand for
Counter electromotive force measured in ohm
Is the amount of induced voltage proportional to the rate of change of current
The amount of induced voltage is directly proportional to the inductance and the rate of charge in a current
Does an inductor oppose a change of current
yes
The current limiting properties of an inductor is called what
Inductive reactance
The resistance of an inductor is similar to that of a resistor but not the same what is the difference
The main difference between the resistance of inductor and a resistor is how they oppose the flow of current
What is the algebraic letter used to indicate inductance reactance and what is the unit measurement used
XL = ohms
In an inductance circuit can the applied voltage ever equal the induced voltage
no
What would happen to the current if the applied voltage was equal to the induced voltage
The current lags the applied voltage by 90 degrees in Purely inductive circuits
What are the three factors that are proportional to determine inductive reactants
The number of turns of a wire, the strength of the magnetic field and the speed of the cutting action
What is the formula for calculating inductive reactants
XL = 2πfL
what is the calculations used to find out how many amps recommend due to inductive reactance
I = E/XL
Can you use the same parallel series for me for solving for L T and X L T in series parallel inductive circuit
yes
In a purely resistive circuit at the exact time when the current peaks the voltage peaks is the voltage and the current considered to be in phase with each other
yes
In a purely inductive circuit how many degrees is the current sine wave delayed compared to the voltage sine wave
90 degrees
Is a purely inductive circuit considered to be leading or lagging
Lagging
What does VARs stand for
Volts amp reactive
Although reactive power in an inductive circuit were essentially no true power is being used we calculated for reactive power in Vars please list the three formulas where EL voltage applied to the conductor IL equals current flow through the inductor and XL equals inductive reactance
Q= EL2/XL
Q = EL x IL
IL = EL/XL
What is the cue of an inductor and what is the formula for calculating Q
Quality of a coil Q = XL/R
Inductors that have a queue of 10 or higher are considered to be what type of inductors
Pure inductors
What is the formula for calculating inductance when we know the inductance reactance and the frequency
L = XL/2πf
The total current limiting effect of resistance and inductive reactance is known as what and what is the letter that symbolizes
Independence Z
What is the formula for calculating independence
Z = ET/IT
When we use the term RL series circuit what is the characteristics of RL and how would we refer to them
When a peer resistive load is connected to an AC circuit the voltage and current are in phase with each other
Why does the voltage drop across the inductor lead the current when the inductor is a pure inductive load
The voltage across an inductor is proportional to the rate of charge of a current through it
In an rl series circuit because the circuit contains both resistive and inductance the voltage and current will be out of phase by some other amount between zero and ninety degrees how is the exact amount of phase angle difference determined
By the ratio of resistance to inductance
Because the resistance is out of phase can we simply just add the inductive reactants and the resistance to give us an RT circuit
No
Describe what VA is or apparent power is
The combination of reactive power and true power is called apparent power and it is the product of circuit voltage and current without reference to phase angle
The relationship between your power and apparent power is referred to as what please include name and abbreviation also why is this an important variable to industry
Power factor PF = %
It defines How efficiently electrical power Is being utilized By the connected load
Why is angle theta important to us
Pops find power factor helps power factor correction impendence calculation voltage and current relationship
Will the same formulas apply to R L parallel circuits as they do R L series circuit
no
Can we use vectors trigonometry or pathogorium theorem to solve for dependence in a parallel circuit like we did in the series circuit
yes The Pythagorean theorem helps to combine the orthogonal components of admittance in series circuits.
This method respects the phase relationships in parallel circuits.
Does this mean that parallel circuits are less likely to
parallel circuits can sometimes exhibit less overall lag compared to series circuit but this depends on the specific value of resistance and inductance
In our homes is there reasonable to believe that we have RL parallel circuits
Yes most home electoral systems are primarily resistive because of light bulbs but inductance components are present like Motors and Transformers
Give one example of an R L parallel branch Circuit in our homes
Refrigerators air conditioners washing Machines
What is a capacitor
Capacitor are devices that oppose a charge of voltage
The simplest type of capacitor is constructed by two different types of metal separated by some insulating materials what is the insulated material called
Dialectric
List the three factors that determine the capacitance of A capacitor
The surface area of the plates the distance between the plates the type of dielectric used
What are the various tasks that capacitor is perform
Filtering coupling timing
Can non polarized capacitors be used in an A C and D C circuit
yes
Polarized capacitors can only be used in what type of circuit
Dc circuit
What does the word polarize mean when referring to capacitors
Polarized capacitors are capacitors that has specific positive and negative terminals
can some capacitors score enough electricity to harm a person even after electronic device is unplugged
yes
What is capacitance
It is the ability of a capacitor to store electrical energy in electric field
How do you capacitors get charged
By connecting it to a D C voltage source
In what form is the energy of a capacitor stored
Electrostatic potential energy
Current will only flow in a capacitor during what two cycles
Charging and Discharging Cycles
What is a leaky capacitor
When energy leaks from these devices is called capacitor leakage
What happens if the dielectric stress becomes too great due to access in voltage applied to a capacitor
Dialectric breakdown
If current is allowed to flow between the plates due to excessively key current because the voltage exceeds rating of the capacitor or the dielectric has to deteriorated what will be the end result for the pasture in the circuit
Permanent Failure: The capacitor will either short-circuit or open-circuit depending on the extent of the damage.
No dielectric that is contained in a capacitor is perfect after. A charge will slowly begin to dissipate through the dielectric what is the effect known as
Dialectric leakage
Dielectric can be found in many different types of insulating material however each material does not have the same amount of capacitance so the material are does not assigned a number what is the number called
Dialectric constant
Vacuum is the reference or control for ganging dielectric constant what is the dielectric constant for vacuum
1
The dielectric constant for vacuum, also known as vacuum permittivity or ε0, is an ideal physical constant with a value of 1
what is the basic unit of measurement used the capacitance of a capacitor and what is the abbreviation symbol used
Capacitor equals farad (F)
A capacitor is considered to have a rating of one farad when what occurs
A capacitor is considered to have a rating of farad when it can store one coulomb of electrical charge while maintaining a potential difference of one volt across its plates
A coulomb is the SI unit of electrical charge for example one coulomb it’s important to not confuse coulomb as a unit with C for capacitance what is the formula for solving the total electrical charge in coulombs
Q=C x V
What is the formula to solve for electric charge when you know the capacitance and the charging voltage
Q = C X V
What is the formula for determining the capacitance of a capacitor
C = Q/V
What is the formula for total capacitance connected capacitors in parallel
CT = C1 + C2 + C3
If I had three capacitors connected in parallel each with a value of 25 U F’s what would capacitance total equal
CT = C1 + C2 + C3
CT = 25UF +25UF + 25UF
CT = 75UF
What are the three formulas for calculating total capacitance for connecting capacitors in series
CT = C1 x C2/C1 + C2
CT = C/N
1/CT = 1/C1 + 1/C2 + 1/C3
If I had three capacitors in Siri each with a value of 25 UF what would the capacitance total equal
1/CT = 1/C1 + 1/C2 + 1/C3
1/CT = 1/25UF + 1/25UF + 1/25UF
CT = 8.3UF
When a resistor is connected in series with a capacitor the capacitor will take some time for it is charged what is the time take for this compaters to charge called
Time constant
How many time constants are there in total to charge a capacitor from zero volts to its rated voltage
It takes about five time constant
So it’s the total time from zero to the capacitor is full or it’s rated voltage is five seconds how much time does each time constant take
1 sec
Where T equals the time it takes for one time constant in seconds r equals resistance in ohms and C equals capacitance in seconds what is the formula used for accurately calculating charging time of a capacitor
t (tau) = R x C
Those the ten different types of capacitors mentioned in this book
Ceramic Capacitors
Dipped Tantalum Capacitors
Film Capacitors
Electrolytic Capacitors
Nonpolarized Capacitors
Polarized Capacitors
Variable Capacitors
Air Capacitors
Supercapacitors
Mica Capacitors
What can happen if you connect a polarized capacitor to a circuit with the incorrect polarity
It will damage or break the capacitor
Is it important to understand each manufacturer’s method of marking polarity capacitance temp coefficient colour codes voltage reading types and ensure you use a correct capacitor for the purpose it was intended
yes
If you have tested your small electric capacitor with your own meter and have no shorts you should test for the kids using variable DC power supply and what other measuring tool
Mostly low scope power supply and ant meter
An A C circuit does the current flow through the capacitor
However, when a capacitor is connected to an alternating current or AC circuit, the flow of the current appears to pass straight through the capacitor with little or no resistance.
In an AC circuit the current alternates in both directions 60 times per second because of its frequency 60 Hertz what physically is happening with regards to the positive and negative plates inside the capacitor
Current flows from one plate to another charging and recharging
The impressed electrostatic voltage that builds up on the plates of the capacitor creates a counter voltage much like the counter voltage observed when using an inductor what is the counter voltage of a capacitor called and what is its symbol
Capacitive reactance XC
In a purely inductive a a C circuit the current is ________ the voltage
Lagging
In a purely resistive AC circuit the current _______is the voltage
In phase with
In a purely capacitive a C circuit the current ____________ is the voltage
Leading
what is the letter of symbol Q referred to regarding capacitors
Quality of a capacitor
If you have a leaky capacitor what will happen to your Q
The dielectric will appear to be much lower resistance and the Q rating will decrease
If you increase the frequency in a purely capacitive circuit the capacitive reactance
It will decrease
In a purely resistive series circuit the current and voltage is in phase which each other in a purely capacitive series circuit current leads the voltage what will the relationship be between the current and the voltage in a series circuit where the we have a resistor and a capacitor in series
The voltage in current will be out of phase between zero to 90 degrees
I said the circuit described in question 17 years was referred to as what
Ratio of resistance to capacitance
In an R C series circuit the current will be _______________the voltage
Lagging
In a parallel RC circuit because the ET = ER = EC the relationship between current and voltage down each individual branch of the circuit will be different in their resistive portion of the circuit the current will be _____________ the voltage
in phase
In a parallel RC circuit because the ET = ER = EC the relationship between current and voltage down each individual branch of the circuit will different in the capacitive portion of the circuit the current will be the voltage
leading
Understanding power factor when looking at the PF of the circuit above at 55.47% would you say that it has a good PF
no
PF is the relationship between true power and apparent power so it will take more power in order to complete the required output from your circuit if you have a low power factor what is the biggest problem regarding a low power factor
The biggest problem with a low power factor is that it results in inefficient use of electrical power. This means the system needs to supply extra power to handle the reactive power, leading to increased energy losses and higher costs. It can also cause overloading of transformers and generators, reducing their efficiency and lifespan.
If you have a poor power factor due to high capacitance leading circuit what can you do
Remove capacitance with a smaller capacitor
If you have a poor power factor due to high inductance lagging circuit what can you do
Add capacitance
