Module 5 Electricity Assignment 1

What is the main danger of static electricity

Arcing

List the factors that affect the severity of electrical shock

-Amount of current

-Path of current

-Type of Voltage

-Voltage Value

-Length of time body is energized

-Condition of your skin

-Area of contact

What three factors affect the electrical resistance of the human body?

-Moisture

-Salt

-Abrasions of the skin

List the five steps taken when rescuing a victim of electrical shock

-Don't touch energized victim

-Free victim of electrical contact

-Apply C.P.R or artificial respiration

-Have someone call for help

-Continue resuscitation attempts

What is the normal maximum voltage-to-ground allowable in the branch circuits of dwelling units?

150 Volts to ground

What is the minimum distance from a gas meter at which are-producing electrical equipment can be installed

900mm- 3ft

0.3048

When locking out equipment, what energy source other than electrical must be taken into consideration?

-Pneumatic

-Hydraulic

-Gravitational

Zero Mechanical state

Are three or four way switches considered to be disconnecting means?

No

Who may remove a lock used to lock out equipment

-Only the person who installed the lock

-In an emergency"supervisor"

What must be obtained before electrical work can be performed on a gas fired equipment

A permit

Which electrical code rules apply to circuits supplying power to heating equipment that uses solid,liquid, or gaseous fules

Rules 26-802 to 26-808

What must be the electrical source for heating equipment rated 400,000 Btu/h and less

The source must be a single branch circuit used for no other purpose

Of what three particles are atoms made?

-Electrons

-Neutrons

-Protons

Which particle carries the basic unit of electrical charge

Electron

How is an atom given a negative charge

By adding electrons

When is an object considered to be electrically neutral

When it has the same number of electrons and Protons

On what does the strength of the forces of attraction and repulsion of an electrostatic field depend

The amount of charge on each object and square of the distance between the objects

List the different ways by which electricity can be produced

-Heat

-Magnetism

-Chemical

-Pressure

-Light

What is produced when electrons are made to move in the same directions

An electrical current

What are the materials called that do not conduct electricity well?

Insulators

What is the term used to describe current that flows in a constant direction

Direct current

What useful effects are produced when electricity flows in a circuit

-Heat

-Magnetism

-Chemical changes

List the three elements required to form an electrical circuit

-An energy source

-Conductors

-A Load

What is the unit used to indicate the strength of electromotive force

Volts

What is the purpose of an electrical switch

It opens or closes an electrical circuit as required

List three electrical circuit protective devices

-Fuses

-Circuit breakers

-Thermal& Magnetic overload

In what unit is electric current measured

Ampares

In what units is the restriction of electric circuits measured

Ohms

State Ohm's Law

The current flowing in an electrical circuit is directing praportional to the applied voltage.

In what units is electrical power measured

Watts or horsepower

What type of circuit allows only one possible path for current flow

Series circuit

The total voltage drop in a circuit must equal what

The voltage of the energy source

What types of circuits allow current to flow through more than one complete path

Parallel circuits

In a parallel circuit, what voltage is applied across each branch

The entire source voltage is applied

List 3 naturally occurring ferromagnetic metals

-Iron

-Nickle

-Cobalt

State the law of Attraction and repulsion

-like poles repel

- unlike poles attract

What is the term used to describe the ease with which a material accepts magnetic lines of force

Permeability

How is the magnetism of an electromagnet increased

By increasing the current flow

What simple rule is used to determine the direction of the magnetic lines of force around a wire

The right hand rule

What is always produces when current flows through a conductor

A magnetic field is produced around the conductor

What is generated whenever a magnetic field moves across a conductor

Voltage

Which type of electrical current flows in both directions

Alternating

List the advantage of alternating current, compared to direct current

-Cheaper to produce

-Can be transmitted over long distance more economically

-Can be easily transformed into lower of high voltages

-Can be transmitted at high voltage to low current

What is the correct name for the AC wave form

Sinusoidal or sine wave

What does a single-phase generator produce

It produces an alternating sinusoidal wave form

Explain the term Impedance

Is the total opposition to the flow of current in a circuit and is comprised of a circuit resistance and reactance

What is the term used to describe the property of an electrical circuit in which a varying current induces an emf in that circuit or an adjacent circuit

Inductance

In purely resistive circuits on what does the resistance depend

-The length

-Cross sectional area

-The material of the conductor

In what units is the apparent power of an electrical circuit measured

Volt-Amperes (VA)

One terminal is always negative, the other always positive. Direction of current flows is constant, reverses only if terminal connections are reversed

Direct current

As it rotates, a voltage appearing at the end of the coil is transferred to an external circuit by slip rings and brushes

AC Generator

Number of current cycles per second

Frequency/Hertz

Used extensively in electronic devices, small appliances. and automobile electrical systems: current flow is always in the same direction

Direct Current

Calculate by determining the effective work done(heat generated) by the electric current

Root means Square

Form is sinusoidal and symmetrical, e.i from zero to maximum positive value, back through zero to maximum negative value, and back to zero; always the same pattern above and below the horizontal axis

Sine Wave

Energy is transmitted throughout the system even though current flow changes direction continuously

Alternating Current

The difference in electrical degrees between two waveforms

Phase

Current flows for 1/120th of a second in one direction and then reverses. Allows electricity to be transmitted over long distances economically

Alternating Current

Movement of a conductor in a magnetic field crosses the flux lines to induce a current. Voltage generated depends on the angle at which the conductor cuts the flux lines

AC Generator

The electrical symbol representative of voltage drop is

VR

The electrical symbol for inductive reactance

XL

The electrical symbol for voltage capacitance is

VC

An R-L electrical circuit is one that has both resistance and

Inductance

In a R-C electrical circuit the current leads the_______ by the _________ somewhere between O Degrees and 90

-Voltage

-Phase

Impedance is measured in _____ It's electrical symbol is ____

-Ohms

-Z

Normally, what color is the insulation on the live conductor in a 120V AC circuit

Black

A conductor having white insulation is normally, connected to the___________ colored terminal on a 120V Ac receptacle

White or Silver

To which winding of a transformer is the current suppied

The Primary Winding

If the number of turns on a secondary winding of a transformer is greater than the number of turns on a primary winding, is the secondary voltage greater or lesser than the primary voltage?

Greater

How is the secondary voltage of a transformer Calculated

By multiplying the primary voltage by the ratio of turns in the secondary to primary coils

what type of transformer has a secondary winding with fewer turns than the primary winding

Step down transformer

Define the term "Self regulating with reference to transformer

Current flow to the secondary winding changes, the primary current flow also changes

What type of transformer consists of a single coil that serves as both primary and secondary winding

Auto- Transformer

What type of electrical meter is used for measuring resistance an continuity

Ohmmeter

What is the purpose of a multimeter

Measure Voltage,Current,Resistance

When using a meter to measure current, how must the ammeter be connected into the circuit

In series with the circuit

Why must an ohmmeter never be connected into a live circuit

Current through the instrument could damage the ohmmeter and possibly cause the battery to explode

What are the steps that must be taken before a multi meter is used to measure voltage or current

-Adjust the zero set

-Select appropriate function

-Select AC or DC

-Make the correct connection to the circuit

-Select the range that gives greatest pointers

Explain the term Linear scale

10 large equal divisions

What is the term used to describe a meter scale that is very cramped on the high resistance end

Non-linear

What does the term VOM standfor in reference to a multi meter

Volts, Ohms, Milli Amps

What allows electrons to flow easily in a circuit

Conductors

What causes resistance to electrons in a circuit

Insulators