Exam 2 Study Guide chapters 1-5

magnetic lines of force are called

flux

wire-wound resistors are often used because they are to operate at ___________ power levels than other resistors

higher

the three substances that form the natural magnets are

iron, nickel, and cobalt

The valence shell of an atom is the

outer shell

An electrical circuit has a voltage of 50 V and a resistance of 5 ohms. What is the value of current

10 amps

A resistor has color bands of brown, black, red, and silver. what is the resistance and the tolerance of the resistor

1000 ohms, 10%

An electric circuit has a resistance of 20 ohms. the current is measured to be 6 A. How many volts are applied to the circuit.

120 volts

A toaster is listed as 1560 W. When it is plugged into a 120 V circuit and starts to make toast, how many amperes will it draw?

13 amps

The Greeks were the first to discover electricity about

2500 years ago

A resistor has a color bands of red, violet, brown, and gold. what is the resistance and tolerance of the resistor

270 ohms, 5%

An electrical device is listed as 3000 watts. Approximately how many horsepower is this

4

An electric motor is running on 120 V. The current is measured to be 2 A. How many ohms of resistance is the motor

60

Current that flows in both directions is referred to as

Alternating current

Nuisance Static Charges

An unintended build up of static electricity. Happens on car and truck as they move through the air, builds on a person as they walk across the carpet, and occurs is a clothes dryer. Mostly on man-made materials.

The lightning protection device that does not connect directly to the object to be protected is called the lightning

Arrestor

An element cannot be chemically subdivided into other elements. The smaller part of an element is a(n)

Atom

Objects charged with different type of chargers will draw toward each other. This is referred to as

Attraction

Current that flows in one direction is referred to as

Direct. Current

The three principles parts of an atom are the

Electron, neutron, and proton

Insulators are the only materials that can hold

Electrons stationary

24 ohms is a standard value for ten percent tolerance resistors

False

A thundercloud cannot contain both positive and negative electric charges.

False

Current always flow from positive to negative

False

the north pole of a compass needle points in the direction of a south geographic pole

False

the word potentiometer comes from the word production

False

The current flow that occurs within a lightning bolt flows

From negative to positive

If a thundercloud has a positive charge, the current in the lightning bolt will flow from the

Ground to the cloud

The neutral conductor is also referred to as the

Grounded conductor

A static electricity charge is an electric charge which

Is not moving

The velocity of AC through a conductor is

Less than the speed of light because magnetic fields travel more slowly in material dielectrics than they do in free air

The most common method of producing electricity is

Magnetism

The unit of resistance to current flow is

Ohm

A conductor is made from a material that contains between

One and three valence electrons

Bringing a charged test object near the ball of a charged electroscope causes the leaves to move close together. This indicates that the test object charge is the

Opposite polarity as the electroscope charge

When an object protected by lightning - is struck by a lightning bolt, it will bleed the lightning discharge to the ground before the protected object can be harmed

Rod

An insulator is a material contains

Seven or eight valence electrons

A(n) - circuit generally occurs when the conductors leading from and back to the power source become connected.

Short

Magnetic North

The direction a compass needle points (in the northern hemisphere) it's also attracted to the south magnetic pole

An electroscope can be used to determine the polarity of an electrostatic charge

True

Lightning is the result of static charges built up in clouds that contain large amount of moisture.

True

Lightning rods provide an easy path to ground for current

True

The application of static electricity is used during the manufacture of sandpaper

True

The discharging of static electricity in thunder clouds creates lightning bolts

True

The grounding conductor is used to help prevent a shock hazard in the event that the ungrounded, or hot, conductor comes in contact with the case or frame of the appliance

True

Voltage pushes current through a wire, but voltage cannot flow through a wire

True

the value of a resistor can often be determined by the "color code"

True

The unit of electrical pressure that causes current to flow is called the

Volt

What is also referred to as electromotive force (EMF)

Voltage

What is used to measure electrical power being used in a circuit.

Watt

A circuit is open, current

Will not flow

A precipitator is a type of _________________.

air filter

Matter has mass and occupies space

always true

the strength of an electromagnet is primarily proportional to its

ampere-turns

a basic law of magnetism states that unlike poles ____ and like poles_____

attract, repel

Alternating current is described as

bidirectional

electrons can form spin patterns that_______ the magnetic field of the material

cancel

a________ resistor is made by applying a film of carbon to a ceramic rod

carbon film

a magnet that produces a magnetic field as long as current is flowing is called a(n)

electromagnet

The part of an atom that has a negative charge is the

electron

magnetism can be explained in terms of _________ spin patterns

electron

Electrical current is the flow of

electrons

resistors that only have one ohmic value are called

fix resistors

The law of charges states that like chargers- and opposite charges

like chargers repel and opposite charges attract

Man-made permanent magnets retain their magnetism _____ than natural magnets.

longer

lodestone is a name for a naturally occurring magnetic material that is also called

magnetite

in the English system, the total force producing a magnetic field is the

magneto motive force

A_________ resistor is made by applying a film of metal to a ceramic rod in a vacuum

metal film

a ________ resistor operates by moving the wiper arm with a screw of some number of turns

multi turn variable

The nucleus of an atom contains

neutrons and protons

if you walk across a carpet, touch a doorknob and get a shock, the shock was the result of a(n)

nuisance static charge

Valence electrons are contained in the

outer shell

____ do not require any power of force to maintain their field

permanent magnets

the measure of a material's ability to be magnetized is called

permeability

The part of an atom that has a positive charge is the

proton

Opposition to current flow is called

resistance

the semiconductor material used as a coating on copy machine drums is

selenium

selenium is a(n)

semiconductor

in a(n) ________ circuit, there is very little resistance and a large amount of current flows

short

the north magnetic pole of of a compass needle is attracted to the

south magnetic pole of the earth

the _________ of a resistor indicates the plus and minus limits of a resistor's ohmic value

tolerance

what does the fourth band of color on a resistor indicate

tolerance

the static charge sometimes used during spray painting is called a(n)

useful static charge

A _________ resistor is made by winding a piece of resistive wire around a ceramic core

wire-wound

A complete circuit is often referred to as a(n)

Closed circuit

In normal operation, current flows through the hot, grounding, and neutral conductors

False

Matter can exist in only two states: solid and liquid

False

A semiconductor contains

Four valence electrons

Electrostatic charges occur on

Insulators

The statement in a DC circuit, the current is directly proportional to voltage and inversely proportional to resistance is know as

Ohm's law

True North

The direction to the geographic North Pole

The precipitator uses a high voltage DC power supply to provide a set of wires with a positive charge and a set of plates with a

Negative charge

The part of an atom that has no charge is the

Neutron

Useful Static Charges

Static electric charges that are intentionally placed on objects

The grounding pong of a plug should never be cut off or bypassed

True

a _________ resistor is made from a compound of carbon graphite and resin bonding material

composition carbon

the angular difference between true north and magnetic north si known as the angle of

declination

if an object is placed in the field of an strong electromagnet connected to an AC line, the object will be

demagnetized

the regions formed in the molecular structure of magnetic metals is sometimes called magnetic __________

domains

in the English system of measure, magnetic strength is measured in a term called

flux density

a _________ resistor is made by combining metal with glass and then applying it to a ceramic base as thick as film

metal glaze

a variable resistor is also called a

potentiometer

a variable with three terminals is called a

potentiometer

The atomic number of an element is the number of

protons in the nucleus

the measure of a material's resistance to magnetism is

reluctance

Objects charged with the same type of charge will push each other away. This is referred to as

repulsion

the amount of magnetism left in a material after the magnetizing force has stopped is called

residual magnetism

a variable resistors with two terminals is called a

rheostat

when a magnetic material's molecules are all lined up, and increases in current flow no longer cause increases in magnetic field strength, the material has reached

saturation

earth contains magnetic poles

true

Direct current is described as

unidirectional

a resistor whose values can be varied over a range of values is called ___________ resistor

variable

______ were used in vacuum-tube circuits many years ago and are still used today in applications involving field-effect transistors (FETs) and multi range voltmeter circuits

voltage dividers