Electrical Flashcards
What are the four distinct states of matter?
solid
liquid
gas
plasma
Matter consists of?
tiny particles called molecules
If protons repel protons and electrons repel electrons what does a proton and a electrons do?
Attract to each other
Molecules are made up of?
combinations of atoms
Protons and electrons exert a force known as?
electric charge
If an object has more protons than electrons it is_______?
positively charged
If there is more electrons than neutrons it is _______?
negatively charged
Electricity is a useful form of energy derived from unbalanced electrical charges in materials. when these charges do not move, they are called _________and they cause attraction or repulsion objects in their close proximity.
static electricity
When the electric charges move in a conductor, the current flow causes magnetic fields around that conductor. all electrical equipment is designed around the interaction of electric and _________ fields?
magnetic
The Law of electric charges states?
- like charges Repel one another
- unlike charges attract one another
what are some common materials for common magnets?
- Steel alloys
- Cobalt
- nickel
- alnico (iron, aluminum, nickel, and cobalt
- platinum and cobalt alloys
- samarium and cobalt alloys
Electromagnetism is?
the interactive relationship between electric charge and magnetic flux
what is a conductor?
a material that exhibits low resistance to current flow, such as copper, silver, gold, aluminum.
what is a insulator?
a material that is a poor conductor of electrical current. Insulators offer a very high resistance to current flow.
glass, mica, dry wood and plastics are all good examples
What is direct current?
If the current flow is always in the same direction. (Dc) fixed polarity.
What are some DC currents?
Portable welder
Car battery
Solar energy cell
Uses of DC power?
-Charging batteries
- operating electrical equipment
- operating dc motors
- welding
- industrial electromagnets
If the current flowing in a circuit from a source of voltage changes polarity (direction of current flow) continuously and regularly it is called?
Alternating current (AC)
What is the standard power line frequency in North America?
60 cycles per second or 60 hertz
_______ refers to single voltage that creates a potential difference between only two conductors.
Single phase
________ refers to three different voltages that interact to produce potential differences between the three conductors that supply the three phase loads. These phases are out of phase with each other by 120 degrees.
Three-phase
The potential differences are between phases:
What are some sources of ac power?
Gas powered alternator
- automobile alternator
- electronic inverter
Voltage can be thought of as?
Electrical pressure
One volt potential difference causes one ampere of current to flow through a resistance of one ohm.
If there is an incomplete path for current to flow it is a ______ circuit?
Open
Current is flowing through a _______ (complete path)
Closed circuit
Series connection
Parallel connection
Series-parallel connection
________ is the property of a material that opposes the flow of an electric current. It is measured in ohms.
Resistance
Why must you take extra caution when working around electricity?
Our senses cannot detect an electrical current
How does electrical shock affect the human body?
Interferes with the normal electrical signals in a human body and can cause the hearts rhythm to dangerously change or to stop
Welding burns are a example of ?
Ultraviolet radiation burn
Safety around electricity involves several elements:
- knowing the hazards
- following safe procedures
- staying alert to what is going on around you
- keeping the work environment clean and safe
- using the necessary safety equipment
When disconnecting a disconnect what is the proper procedure?
- stand on the same side as the switch
- turn body away from the box
- throw the switch with the non dominant hand
Follow these steps to lock out control power:
- find out how and where unit is controlled.
- find the disconnect that serves the area you need to service
- make sure power source is not interlocked with another part of the process
- of the controls are on a large console and there is a control power key, turn the key off.
- if provided place key in a lockbox
Before opening the electrical enclosure that has been locked off you must?
Test start
What is the purpose of a fuse?
Limit maximum current flow to a safe level during a short circuit failure or heavy sustained overloads
How does a fuse blow?
A fusible link is in the fuse barrel. The link melts when the current exceeds the design par-meters.
What are some advantages of PLC’s
- lower overall cost
- programmability
- reliability
- expandability
