Electrical Safety and Fundamentals Quiz

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

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!