Electrical Safety and Fundamentals Quiz

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Questions and Answers

Approximately how many workplace deaths related to electrical incidents occur each workday?

More than one (correct)

Two or more

Around one

Less than one

What is the main cause of secondary injuries from electrical shock?

Direct burn from heat

Involuntary muscle reactions (correct)

Internal organ damage due to electricity

Exposure to high voltage power

Which of these is NOT an effective way to avoid electrical injuries in work places?

Ignoring emotional distractions

Being focused on the task

Being alert to potential hazards

Taking shortcuts to complete tasks faster (correct)

What are the fundamental components of an atom?

Protons, neutrons, and electrons Signup and view all the answers

What type of electrical charge do electrons possess?

Negative charge (-) Signup and view all the answers

What creates an electrical flow?

The movement of free electrons Signup and view all the answers

What force binds electrons to their orbit around the nucleus?

The attraction of protons Signup and view all the answers

How can an electron become a ‘free electron’?

By applying an external force like friction Signup and view all the answers

What is the term for the total opposition to current flow in an AC circuit containing both reactance and resistance?

Impedance Signup and view all the answers

In a purely inductive AC circuit, what is the phase relationship between voltage and current?

Voltage leads current by 90 degrees Signup and view all the answers

What is the relationship between frequency and capacitive reactance?

Inversely proportional Signup and view all the answers

In a purely capacitive circuit, what is the phase relationship between current and voltage?

Current leads voltage by 90 degrees Signup and view all the answers

If an AC circuit has both resistance and inductive reactance, by how much does the voltage lead the current?

More than 0 and less than 90 degrees Signup and view all the answers

What is the term for the opposition to current flow in an AC circuit caused by inductance?

Inductive reactance Signup and view all the answers

In a purely resistive circuit, what is the phase relationship between current and voltage?

Current and voltage are in phase Signup and view all the answers

What is the unit of measurement for reactance and impedance?

Ohms Signup and view all the answers

What is the nature of power delivered to a circuit by the source, that is not consumed?

It is all returned to the source. Signup and view all the answers

What is the term for the power delivered by the source in an AC circuit?

Apparent power Signup and view all the answers

What form of energy does the true power dissipate in a circuit?

Heat Signup and view all the answers

According to the table of content provided, on which page can information about 'Contact "normal" state' be found?

Page 74 Signup and view all the answers

What is the primary function of an electrical switch?

To interrupt the flow of electrons Signup and view all the answers

What are the two fundamental states of a switch?

Open and Closed Signup and view all the answers

What was the main reason given for covering switch types at a later stage of the book series?

The chapters that follow explore older digital technology based on mechanical switch contacts. Signup and view all the answers

What is the simplest kind of switch described in the content?

A switch where two electrical conductors contact each other by motion. Signup and view all the answers

What is the 'normal' condition of a speed switch?

Shaft not turning Signup and view all the answers

Which of these is an example of a normal state for a temperature switch?

Ambient (room) temperature Signup and view all the answers

A level switch's 'normal' state is when the tank or bin is:

Empty Signup and view all the answers

What condition describes a flow switch in its 'normal' state?

Zero liquid flow Signup and view all the answers

In its normal state, what is the condition of a normally-open switch contact?

Open, not allowing current to flow Signup and view all the answers

In a schematic diagram, how is a normally-open generic switch contact designated?

Two vertical lines separated from each other Signup and view all the answers

What is another name for a normally-open, on-delay contact?

Normally-Open, Timed-Open Signup and view all the answers

In a NOTO contact, when does the timing action occur?

Upon de-energization of the coil Signup and view all the answers

When is an NCTO contact normally closed?

When the coil is unpowered Signup and view all the answers

What causes an NCTO contact to open?

The application of power after a set amount of time Signup and view all the answers

What is the primary function of a shading ring in an AC solenoid?

To increase the minimum pull on the armature. Signup and view all the answers

What is the function of an optocoupler in a solid-state relay?

To achieve electrical isolation. Signup and view all the answers

What is a key characteristic of a latching relay?

It remains in its last state when power is switched off. Signup and view all the answers

How can a latching relay be switched in a two-coil design?

By a pulse to one coil to switch on and a pulse to the opposite coil to switch off. Signup and view all the answers

What is the main purpose of a lockout relay?

To maintain associated equipment out of service until reset. Signup and view all the answers

What protects the contacts in a reed relay?

A vacuum or inert gas filled glass tube. Signup and view all the answers

Which of the following is a common characteristic of reed relays?

They are capable of faster switching speeds than larger relays. Signup and view all the answers

What distinguishes a mercury-wetted reed relay from a standard reed relay?

Its contacts are wetted with mercury. Signup and view all the answers

Study Notes

JADEER LEARNING MANUAL ELECTRICAL AREA 2

This manual is for general business use
Contains information on plant electrical installation level 1
Job/Area: Electrical Technician, Area 2
Reference #: JAD-LC-A2-YP-EMT-LM
Module #: 2024
Revision #: 2024.01
Issue Date: 6 Nov 2024
Next Review Date: 01 Oct 2027

BASICS OF ELECTRICITY

Basic introduction of electricity
DC and Magnetism
Understanding of AC Circuits
Series and Parallel Circuits
Understanding of Electrical Formulas
Understanding of Power Triangle

COMMON ELECTRICAL HAZARDS

Electricity is dangerous
Statistics show a high number of employee injuries and fatalities

BASIC INTRODUCTION OF ELECTRICITY

All matter is composed of molecules made of atoms
Atoms have a nucleus with electrons orbiting around it
The nucleus is composed of protons and neutrons
Electrons have a negative charge
Protons have a positive charge
Neutrons are neutral

CONDUCTORS

Materials allowing many free electrons to move freely are called conductors
Copper, gold, silver, and aluminum are good conductors
Copper is widely used as conductors due to being relatively inexpensive

INSULATORS

Materials that allow few free electrons are called insulators
Plastics, rubber, glass, mica, and ceramic are good insulators
Insulators are used to keep electrons in conductors

ELECTRIC CHARGES

Elements are defined by the number of electrons in orbit and the number of protons in the nucleus
An atom with an equal number of electrons and protons is electrically neutral
Electrons in the outer band can be forced out of their orbit

CURRENT

Electricity is the flow of electrons in a conductor from one atom to the next in the same general direction
Current is measured in amperes (amps)

VOLTAGE

Voltage is the force required to make electricity flow through a conductor
Measured in volts

RESISTANCE

Resistance is the property of a circuit, component, or material that opposes current flow
Resistance depends on composition, length, cross-section, and temperature of resistive material

OHMS LAW TRIANGLE

Ohm's Law can be expressed in three easy ways in a triangle
If two values are known, the third value can be easily calculated

BASICS OF ELECTRICITY (DC AND MAGNETISM)

Magnetism principles are an integral part of electricity
Invisible magnetic lines of flux leave the north and enter the south pole of a magnet

ELECTROMAGNETISM

A magnetic field is generated by current flow in a conductor
An electric current creates a magnetic field
A left-hand rule can apply to determine the direction of magnetic lines of flux

ELECTROMAGNETS

A coil of wire carrying a current acts like a magnet
The strength of an electromagnet can be increased by adding more turns to the coil, or increasing the amount of current, or by winding the coil around a material that conducts magnetic flux more easily

UNDERSTANDING OF AC CIRCUITS AC CURRENT

Alternating current (AC) is used a lot
AC continuously changes direction
A sine wave can represent current or voltage

BASIC AC GENERATOR

A basic generator consists of a magnetic field, an armature, slip rings, and brushes
The armature rotates through the magnetic field
A voltage is thus generated in a conductor as it moves through the field

FREQUENCY

The number of cycles per second of voltage induced in the armature is the frequency
Hertz (Hz) is used as a unit of frequency
60 Hz is a common frequency used in the United States and Saudi Arabia

FOUR POLE AC GENERATOR

The frequency will be the same as the rotations per second when the magnetic field is produced by only two poles
The poles will increase the number of cycles completed in a revolution

AMPLITUDE

Amplitude is the range of variation for a sine wave, which represents the current or voltage
A sine wave has three ways of describing amplitude: peak value, peak-to-peak value, and effective value

INSTANTANEOUS VALUE

The instantaneous value is the value at any one point on the sine wave

INDUCTIVE REACTANCE

Inductive reactance is the opposition to current flow in an AC circuit due to inductance
Measured in ohms

CURRENT AND VOLTAGE PHASES

In a purely resistive circuit current and voltage rise and fall at the same time
In a purely inductive circuit, voltage leads the current by 90 degrees

CAPACITIVE REACTANCE

Capacitors oppose current flow in an AC circuit
Capacitive reactance is inversely proportional to frequency and capacitance

CALCULATING IMPEDANCE

Impedance (Z) is the total opposition to current flow in an AC circuit
Represented as a vector with magnitude and direction

SERIES R-L-C CIRCUIT

Many circuits contain values of resistance, inductance, and capacitance in series
Current can lag voltage by 90 degrees in an inductive AC circuit
In a capacitive AC circuit current leads voltage by 90 degrees
Total impedance of a circuit is the resistance plus or minus the reactance

PARALLEL R-L-C CIRCUIT

Many circuits contain values of resistance, inductance, and capacitance in parallel
In an inductive AC circuit current lags voltage by 90 degrees
In a capacitive AC circuit current leads voltage by 90 degrees

TRANSFORMERS

Electromagnetic devices that transfer electrical energy from one circuit to another by mutual induction
Used to step up or down voltage
Has two coils: a primary coil and a secondary coil

TRANSFORMER TURNS RATIO

There is a relationship between primary and secondary voltage, current, and impedance

RESIDENTIAL TRANSFORMER APPLICATIONS

The most common power supply system used in residential applications in the United States is single-phase, three-wire
120V is used for general purpose receptacles and lighting
240V is used for high demand (heating, cooling, cooking)

THREE-PHASE POWER

Used where power demands are higher (commercial and industrial applications)
Three overlapping AC cycles

THREE-PHASE TRANSFORMERS

Three-phase transformers require three interconnected coils in both the primary and secondary

POWER IN AC CIRCUIT

Power is dissipated as heat in resistive circuits (true power)
Measured in watts(W)
The rate of non-working energy is reactive power
Measured in VAR (Volt-amperes Reactive)
Apparent power is the total of true power and reactive power (Measured in VA)

POWER FACTOR

The ratio of true power to apparent power in an AC circuit
Cosine of the phase angle (between voltage and current)

SERIES CIRCUIT RESISTANCE

Resistors are connected end-to-end with only one path
Total resistance is the sum of the individual resistor values

SERIES CIRCUIT VOLTAGE AND CURRENT

The total current in a series circuit is determined by dividing the source voltage by the total resistance
The voltage across a resistor is the voltage drop, and the sum of the voltage drops adds up to the source voltage

PARALLEL CIRCUIT RESISTANCE

Parallel circuits have multiple paths for current flow
Total resistance is reciprocal of individual resistances added then reciprocal of the added results

PARALLEL CIRCUIT CURRENT

Circuit voltage divided by branch resistance to determine branch current
Total current is the sum of currents of the branches

GENERAL SYMBOLOLOGY

Different switch types have different symbols

CONTACT "NORMAL" STATE AND BREAK SEQUENCE

Normal switch position describes the off state of a circuit
Normally open contact means the circuit is open when de-energized, closing upon activation
Normally closed contact means the circuit is closed when de-energized, opening upon activation

BASIC DESIGN AND OPERATION

Relays are adaptations of electromagnets
Includes coil, armature, and contacts
A magnetic field is generated by current in a coil
The magnetic field attracts an armature , which causes the contacts to operate either fully on or fully off

RELAY TYPES

Latching (keep) relays remain in their last state after power is removed
Lockout relays are used to mechanically or electrically protect equipment

REED RELAY

Reed relays use contacts inside a vacuum or inert gas filled glass tube
Magnetic field operation opens/closes contacts

MERCURY-WETTED

Contacts are wetted with mercury
Used for low-voltage applications due to their low contact resistance and fast switching speeds

MACHINE TOOL RELAY

Standardised electrical control for machine tools
Features many contacts for multiple operations

SOLID-STATE RELAY

No moving parts, higher reliability
Uses transistors for switching

BUCHHOLZ RELAY

Safety device mounted on oil-filled transformers and reactors
Detects internal problems
Detects gas or low oil levels from leaks or ruptures

TIME-DELAY RELAYS

Delay the operation of a circuit or switch based on a specified amount of time
Commonly used to control circuits, such as motors or pumps.

DIGITAL LOGIC FUNCTIONS

Boolean algebra, Boolean operators to perform logic functions
AND, OR, and NOT gates
Logic circuit components

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Description

Test your knowledge about electrical safety, workplace incidents, and the fundamental principles of electricity. This quiz covers various topics including electrical charges, circuit behavior, and the anatomy of an atom. Perfect for anyone studying electrical safety or electronics!