Week 2 Electrical Flashcards
Conductivity ratings are compared to that of what metal which has a rating of what?
silver at a 100 rating
protons and electrons exert a force known as?
electric charge
the four distinct states of matter are?
solid liquid gas and plasma
Nearly all atoms have some electrons that are loosely bonded around the nucleus and these can be readily knocked loose. these are called ?
free electrons
when the electric charges move in a conductor, the current flow causes?
magnetic fields around that conductor
the ease with which a material can be magnetized by a solenoid is a measure of its?
permeability
when electricity is sent to the semiconductor what can happen?
their state can change from conductive to non conductive or vice versa.
in a three phase load the phases are how far out from each other?
120º
For an electric current to flow, there must be a ______ between two points of the supplying device.
potential difference
the potential difference between two points of the supplying device is called and is measured in what?
voltage volts
____ is the rate of flow of electrons (current flow) in an electrical circuit.
amperes (amps)
_____ is done when a force overcomes an opposing resistance.
work
_____ is having the potential to do work.
Energy
______ is the rate at which work is done.
power
1 hp is how many watts?
746 watts
_____ is the property of a material that opposes the flow of an electric current?
Resistance
resistance is measured in?
ohms
The movement of free-electrons can be forced to drift in the same general direction, then they constitute what is called an _____.
electric current
How are the electrons of an atom held in orbit?
Electrons carry a negative charge. protons carry a positive charge. They are held in those orbits by the force of attraction between opposite electric charges.
elements with 4 electrons in there outer valence shell are?
semi conductors
elements with more than 4 electrons in there outer valence shell are?
insulators
elements with less than 4 electrons in there outer valence shell are?
conductors
When current flows, a ___________ is set up around
the current path.
magnetic field
When current flows, certain chemical changes may occur. This is made use of in?
corrosion, and electroplating as in batteries.
When current flows through a conductor, the _____ of that conductor rises. This effect is made use of in _______.
temperature. electric heating and lighting.
name the effects that can be used to detect the presence and magnitude of an electric current.
heating, magnetic, and chemical.
If the molecules in a metal can be aligned so that their individual magnetic fields all act in the same direction, then the metal become a ______.
magnet
What materials are used to produce temporary magnets?
iron and silicon steel
What materials are used to produce permanent magnets?
steel or steel alloys containing nickel and cobalt
A fundamental law of magnetism states that:
Like poles repel, and unlike poles attract.
current flow is measured in _____?
ampere
potential is measured in _____?
volts
resistance is measured in ______?
ohms
The _____uses electrical energy to do useful work.
load
What types of circuits are used in electrical work?
series, parallel, series/parallel, and complex.
what is the most common type of circuit?
Parallel circuits
______ circuits are connected so that the same potential-difference (voltage) appears across each load.
Parallel
______ circuits are connected in such a way that the same current flows through each load.
Series
At a given temperature, the current flowing through a conductor is directly proportional to the voltage across that conductor. this is?
Ohm’s law
As the temperature of conductors increase. this changes the resistance in the circuit how?
it also increase
As the temperature of most common insulators increase, how does this effect resistance?
it reduces it.
What is defined as energy in transit from one form into another. 2 - 40
work
what is equal to voltage times current times time?
Electrical work
what is defined as the rate of doing work?
Power
what is power measured in?
watts
what is energy and work measured in?
joules
If the secondary winding has fewer turns than the primary winding, then the voltage induced into it is _____. The transformer is then termed a _____ transformer.
lower
step-down
If the secondary winding has more turns than the primary winding, then the voltage induced into it is ______. The transformer is then termed a _____ transformer.
higher
step-up
Lighter loads (such as lighting circuits) are connected between either line to line, or line to neutral, and are Subjected to how many volts.?
line and neutral
120 V
Heavier loads (like clothes dryers) requiring more energy are connected between either line to line, or line to neutral and are subjected to how many volts?
line and line
240 V
how are three-phase generators winding connected?
wye (star) or delta (mesh)
how many conductors does delta (mesh) connectors take in a three-phase generator?
3 conductors
how many conductors does wye (star) connectors take in a three-phase generator?
4 conductors
How is the direction of rotation changed in a three-phase induction motor?
the direction of the rotating field can be reversed by interchanging any two of the three line conductors that supply the motor.
If free electrons can be forced to drift in the same general direction, they are called?
Electric current.
If electric current travels in one direction, it is?
Direct current
If the generator has two poles, the sine wave would be created in how many degrees?
360 degrees
If the generator has four poles, the sine wave would be created in how many degrees?
180 degrees
The number of cycles an alternating current generates per second is known as?
Frequency
Frequency is measured in?
HertZ
The cross sectional area of a conductor is measured in?
Circular mils
If the area of the conductor is doubled the resistance is?
Halved
As length of the conductor doubles the resistance?
Doubles
Name three factors that affect inductance.
Material, the frequency, and the amp turns.
What frequency do Standard power lines in North America run at?
60 hertz
As frequency increases, how does the inductive resistance of an inductor change?
It also increases.
What does a cycle on a sine wave look like?
It starts at 0 hits maximum positive hits maximum negative then returns to 0.
What does amp turn refer to?
The number of windings.
True or false
If the molecules in a metal are not aligned, then the metal does not act as a magnet
True.
What are The Fields of force around a magnet?
magnetic Flux lines
In ohms law E = I X R, what are the abbreviations?
E is potential difference ( volts).
I represents rate of current flow ( amps).
R represents opposition to current flow or resistance (ohms).
At what angle are Electricity and magnetic fields at to each other?
Right Angle.
Name four ways to increase induced voltage.
- Increase the strength of the Magnetic field,
- increase the number of conductors that are breaking the flux lines.
- increase the speed of relative motion.
- increase the angle between the flux lines and the conductor.
What is the maximum angle a conductor has to be to achieve maximum voltage in a induction field?
90 degrees
What is relative motion?
a connection between electric and magnetic fields affecting each other.
Name some 1st class levers.
Teeter-totter. Oars on a boat. Catapult. Shoehorn. Scissors. Pair of pliers.
Name some 2nd class levers.
wheelbarrows, staplers, bottle openers, nut cracker, nail clippers.
What is stationary electric charge called?
Static electricity
What is a moving electric charge called?
Electrical current
Define a magnetic flux
The entire Magnetic field surrounding a magnet
What are the three principles of electromagnetism?
Moving electrically charged particles create magnetic fields.
Magnetic fields attract or repel moving charged particles.
Moving magnetic fields near charged particles causes current flow.
When a voltage is generated by a magnetic field moving through a conductor that voltage is known as?
An induced electromotive force, EMF.
No voltage is induced when the conductor is traveling in which direction to the lines of flux?
Parallel
When referring to electrical loads, a phase is an instant in time on a sine wave and is measured in what?
degrees of rotation
what is the alternating current wave called?
sine wave
what does alternating current mean?
Alternating current changes direction regularly and continuously.
what does direct current mean?
direct current always flows in the same direction.
what is the current caused to flow in a EMF?
Induced current.
Name a semi conductor material.
germanium, gallium arsenide and silicon
Name a insulator material.
Glass, mica, plastics
Name a conductor material.
Gold, silver, copper
list a use of a electromagnetic device
solenoid valves
electric motors
scrap metal lifting magnets
electric brakes
Name a use for direct current
electronic equipment
operating dc motors
industrial electromagnets
welding
name a source of direct current
direct current generators
batteries
what does dielectric mean?
A dielectric is an electrical insulator that can be polarized by an applied electric field.
Explain the basic construction of a capacitor.
two conductor plates sandwiching a insulator
what are the three ohms equations?
E = I * R I = E / R R = E / I
in a conventional theory current flows how?
positive to negative
The flow of electrons is termed electron current. Electrons flow in which direction?
negative terminal to the positive
true or false
can magnetic flux line be insulated.
false, air is the best.
in a conventional theory the magnetic field flows how?
counter clockwise from a right angle to the flow of current
in a electron current theory the magnetic field flows how
clockwise from a right angle to the flow of current
true or false
The current or amps in a series circuit is the same at all places in the circuit.
true
true or false
The supply voltage is split up between components in a series circuit.
True, it shared.
true or false
The voltage across components in parallel is the same for each component.
true
True or false
A parallel circuit has two or more paths for current to flow through.
True.
Name the three rules of series circuit
The amount of current is the same through any component in a series circuit.
The total resistance of any series circuit is equal to the sum of the individual resistances.
The supply voltage in a series circuit is equal to the sum of the individual voltage drops.
Name the three rules of series circuit
The amount of current is the same through any component in a series circuit.
The total resistance of any series circuit is equal to the sum of the individual resistances.
The supply voltage in a series circuit is equal to the sum of the individual voltage drops.
Name the four rules of a parallel circuit.
A parallel circuit has two or more paths for current to flow through.
Voltage is the same across each component of the parallel circuit
The sum of the currents through each path is equal to the total current that flows from the source.
If one of the parallel paths is broken, current will continue to flow in all the other paths
True or false
The sum of the resistors in a parallel circuit is the total resistance?
False
True or false
The total resistance in a parallel circuit is always less than any of the branch resistances.
True
True or false
Adding more parallel resistances to the paths causes the total resistance in the circuit to increase
False, it decreases.
True or false
As you add more and more branches to the circuit the total current will increase.
True, because Ohm’s Law states that the lower the resistance, the higher the current.
True or false
Work is the force that causes current to flow through an electrical conductor.
False, Voltage does.
What does Cetane rating refer to?
The ability for diesel fuel to ignite.
When compared to winter diesel fuel, the BTU content of summer diesel fuel is what?
Higher
What can be added to a diesel fuel tank in small amounts to prevent the formation of ice crystals when temperatures drop below freezing?
Isopropyl alcohol
Fuel tanks should be vented to prevent?
A vacuum from forming in the tank during supply.
The term cloud point refers to the
Temperature at which waxes (paraffins) become solids in the fuel.
Flash point means
The self ignition temperature of a fuel.
True or false
Simple AC Generators need a fluctuating RPM to maintain Frequency (60 Hz).
False, they need to maintain a constant rpm.
True or false
DC is produced either directly off the commutator or the brushes.
True.
In a generator typically what creates the regulating magnetic field?
The rotor.
In a generator current is created and drawn off what?
fixed stator windings
In a generator what part does the voltage regulator control the current flow through?
The rotor.
True or false
A generator works by having a rotor inside the generator which is turned by a belt and drive pulley which are turned by a engine.
True
The magnetic field of the rotor generates a current in the stator windings by what?
Electromagnetic induction.
True or false
A fault in a series portion of the circuit would affect the operation if the series part was in the power or the ground side of the parallel portion of the circuit
True
True or false
A fault in a series portion of the circuit would affect the operation if the series part was in the power or the ground side of the parallel portion of the circuit
True
True or false
A fault in one leg of a series-parallel circuit will affect all the components in the circuit.
False, it will only affect just the components in that one leg.
“The current flowing into any junction of an electrical circuit is equal to the current flowing out of that junction.”
This is which law?
Kirchhoff’s current law
Relays contain a coil and when power is removed, the magnetic field surrounding the coil collapses, creating a voltage to be induced in the coil winding.
Relay Voltage Spike Control
True or false
A short-to-voltage involves a copper-to-copper connection and usually affects more than one circuit.
True
True or false
A short-to-ground involves a copper-to-Cooper connection and usually causes the fuse to blow
False, it usually involves Cooper to steel
What is the main difference between a propane tank and a propane cylinder?
The standards and approval agency responsible for certification.
What is the minimum rated working pressure for a propane tank?
250 psi
How far must weeds and long dry gras or other flammable materials be kept clearof a propane tank?
10 feet
What part of a propane tank may be field-welded?
Saddle plates or brackets
What part of a propane tank may be field-welded?
Saddle plates or brackets
What must be attached to a pressure relief valve installed in a propane tank?
a loose-fitting rain cap to prevent rain and snow from entering the valve
