Chapter 1: Electrical Basics Flashcards
What is Electricity?
An invisible force that can produce heat, motion, light, and many other physical effects.
Electricity, electron, and electronics are English words that come from a word with a Greek background, what is that word?
Elektron, which means “to be like amber”
In the 1600’s who coined the terms electriks and non-electriks?
William Gilbert
What are Electriks and Non-Electriks?
Electriks are materials that could be charged
Non-electriks are materials that could not be charged
In 1733, Charles DuFay discovered
some charged materials would attract other objects and that other charged objects would repel different objects.
What is the purpose of Ohm’s Law?
Describes in detail the Mathematical relationship among Voltage, Current, and Resistance in a simplified form.
In Ohms Law nomenclature “I” is ________, “E” is ________ and “R” is ________
Current
Voltage
Resistance
The Letter “I” represents ______ and is evolved from the notion ?
, it is measured in ?
Current
that it was representative of the intensity of flow, measure in Amperes
The Letter “E” or “V” represents ______ and evolves from the abbreviation ? , and is measured in ?
Voltage
Electromotive Force measures in Volts
The Letter “R” represents ?, and is measured in ?
resistance to current flow in the circuit
measured in ohms
What is the basic premise/concept of Electricity?
The movement of Electrons that have been activated or energized by an external energy. That external energy is imparted to the electrons, which “flow in a conductor”. The electrons give up their energy at an electrical load as they produce heat, light, motion, etc.
How do we measure the flow of electrons?
Electrons are measure in coulombs per second at a fixed point.
What is a coulomb?
6.25 x 10^18 electrons. This is the fixed quantity of electrons that move past a certain point per second.
One coulomb is equal to how many amps?
1 amp
An Ampere is equivalent to
1 coulomb of electrons flowing past a specific point in a wire in 1 second.
What charge does an electron have?
Negative
In a battery, the negative terminal is
where there is an excess buildup of electrons due to their negative charge.
Outside the battery, the electrons travel
from the negative terminal through each circuit component and back to the positive terminal.
Inside the battery, the electrons move
from the Positive terminal to the Negative terminal.
What tool is used to measure the amount of current flow in a circuit?
An ammeter
How does an Ammeter work?
As current flows through a circuit, it will flow through the meter’s movement. The movement responds to the magnetic field created by the current flow.
When measuring with a Analog Ammeter what must you do to obtain an accurate reading, when measuring current?
Begin with the highest scale on the meter and then decrease the scale to obtain the proper reading.
What is Conventional Current Flow?
The flow of electrons from the Positive Pole to the Negative Pole of a DC source.
What is the concept of Conventional Current Flow?
An electron leaves an atom, causing the atom to become more positively charged. This creates a hole, this hole is then filled with an Electron from a neighboring atom. As electrons move in one directions, the Hole moves in the opposite direction.
Current in a conductor travels at what speed?
Less than the speed of light. Often 80%
Electromotive Force is
A potential difference in electron charges
What does a Potential difference mean?
When one object has greater or fewer number of electrons than another object.
The volt is defined
amount of potential that will cause 1 coulomb to do 1 joule of work
One Joule is
the amount of energy equal to .737 foot pounds
Voltage causes
Current to flow
A volt meter is the means
of measuring the potential difference, or difference in pressure in a circuit.
Current is present when both ? and ? are present
Both a voltage source and current path are present
Voltages and Currents are polarized. True or False?
True
Most Voltmeters measure voltage by
drawing a very small amount of current from circuit being tested.
What is the Ohm?
The measurement of the amount of opposition to current flow that exists in a circuit object.
What is the statement of Ohms law?
1 ohm is the amount of resistance in a circuit that allows 1 ampere of current to flow when a potential of 1 volt is applied.
The Greek symbol _______ is used for Ohm.
Omega
A material that has many free electrons has ? resistance? And is called a ________
Low
Conductor
A material that does not have many free electrons is called a _______? It has ________ resistance?
Insulator
High
For a circuit to be complete it must have what three things?
A source to provide the force needed for electrons to flow
A supply path from the source to the load
A return path from the load to the Original source.
When current flows, you have a ______ circuit.
Closed
When there is no current flow, you have a _______ circuit.
Open
What is the definition of a short circuit?
Current has found a shorter path back to the source, bypassing all resistance elements in the circuit. This causes maximum current. the source shuts down.
The unit of power is ________
Watt
What is Power in an electrical circuit?
Power is the amount of work being done per unit of time.
What is consumed when a voltage is applied to a circuit and current flows through the load?
Power
For power to exist in an electrical circuit, what must take place?
The load in the circuit converts electrical energy supplied into some other form of energy.
The circuit becomes hotter due to
more current that is allowed to flow
If current is doubled the heat produced
increases four times
If current is tripled the heat produce goes up
Nine times
The heat produced by the current through the resistance in a circuit is referred to as __________, _________, _________
I^2R Losses
Watt Losses
Power Losses
What is the Joule?
Unit of energy used to measure the heat or work produced or consumed in a system.
What is the work used in heating a circuit called?
Lost Work
In terms of harm, Electricity can create what four things?
Electrocutions
Arc blast and burns
Ignite Combustible vapors
Heat materials to a point that creates cumbustion
OSHA places the threshold voltage of electric shock at?
50 volts
In a Lock out, Tag out situation who must remove your Lock?
Yourself
Arch Flashes create extreme heat temp up to?
35,000 degrees Fahrenheit
Flash protection boundary means what?
Distance referred to how far you must be from a Flash incident to get a “Just Curable” burn.
What type of protection is used to protect Wiring devices and materials?
Fuses and Circuit Breakers
What type of protection is used to protect personnel in an electrical circuit?
Circuit Interrupters
How does a GFCI work?
The device monitors the amount of current entering the load and leaving the load. If the difference is greater than the rating (usual 5mA) the device will open the circuit.
How do Arc Fault Circuit Interrupters work?
The device is installed at the Panel. It is designed to determine if there is in arc in the circuit that could start a fire. I.e. pinch cord.
This arc could be small enough to not trip a regular circuit breaker because of the lack of necessary current.
how many watts are equivalent in 1 horsepower?
746 Watts
One joule is the amount of energy used when ? is lifted a distance of one foot.
.737
