DC Midterm

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

270 , 5%

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

Ohm's

A precipitator is a type of _____.

air filter

Current that flows in both directions is referred to as _____ current.

alternating

The _____ is equal to one coulomb per second

ampere

The strength of an electromagnet is primarily proportional to its _____.

ampere-turns

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 smallest part of an Element.

atom

A basic law of magnetism states that unlike poles _____ and like poles _____.

attract, repel

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

attraction

Alternating current is described as _____.

bidirectiona

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 complete circuit is often referred to as a(n) _____ circuit.

closed

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

composition carbon

What is the term for an amount of charge equal to 6.25 x 1018 electrons?

coulomb

The angular difference between true north and magnetic north is known as the angle of _____.

declination

Current that flows in only one direction is referred to as _____ current.

direct

The regions formed in the molecular structure of magnetic metals is sometimes called magnetic _____.

domains

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

electromagnet

Magnetism can be explained in terms of _____ spin patterns.

electron

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

electron

The three principle parts of an atom are the _____.

electron, neutron, and proton

Electrical current is the flow of

electrons

Insulators are the only materials that can hold _____ stationary.

electrons

Resistors that only have one ohmic value are called _____ resistors.

fixed

Magnetic lines of force are called

flux

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

flux density

A semiconductor contains _____ valence electrons.

four

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 _____ conductor.

grounded

An opposition to current flow that occurs in alternating current circuits is called _____.

impedance

Electrostatic charges occur on

insulators

The three substances that form natural magnets are _____.

iron, nickel, and cobalt

A static electric charge is an electric charge which _____ moving.

is not

To locate the north pole of an electromagnet, use the _____ hand rule.

left

The velocity of AC through a conductor is _____ the speed of light because magnetic fields travel more slowly in material dielectrics than they do through free air.

less than

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

longer

The most common method of producing electricity is

magnetism

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 _____.

magnetomotive force

A _____ resistor is made by applying a film of metal to a ceramic rod in a vacuum.

metal film

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

metal glaze

A _____ resistor operates by moving the wiper arm with a screw of some number of turns.

multiturn variable

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 _____ charge.

negative

The part of an atom that has no charge is the

neutron

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) _____ static charge.

nuisance

The static charge that accumulates on clothes in a dryer is a(n) _____ charge.

nuisance

The valence shell of an atom is the _____ shell.

outer

Valence electrons are contained in the _____ shell.

outer

The measure of a material's ability to be magnetized is called _____.

permeability

A variable resistor is also called a

potentiometer

A variable resistor with three terminals is called a _____.

potentiometer

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

proton

The atomic number of an element is the number of _____ in the nucleus.

protons

The measure of a material's resistance to magnetism is

reluctance

Opposition to current flow is called _____.

resistance

A variable resistor with two terminals is called a _____.

rheostat

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

rod

When a magnetic materials molecules are all lined up, and increases in current flow no longer cause increases in magnetic field strength, the material has reached _____.

saturation

The semiconductor material used as a coating on copy machine drums is _____.

selenium

Selenium is a(n)

semiconductor

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

short

In a(n) _____ circuit, there is very little resistance and a large amount of current flows.

short

The north magnetic pole of a compass needle is attracted to the _____ magnetic pole of the earth.

south

Direct current is described as

unidirectional

The static charge sometimes used during spray painting is called a(n) _____ static charge.

useful

A resistor whose values can be varied over a range of values is called a _____ resistor.

variable

The force of electrostatic attraction or repulsion is directly proportional to the product of the two charges and inversely proportional to the square of the distance between them. This is _____ law.

Coulomb's

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

demagnetized

The unit of resistance to current flow is the _____.

ohm

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

An insulator is a material containing _____ valence electrons.

seven or eight

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

10 A

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

1000 , 10%

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

120

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

An electrical device is listed as 3,000 watts. Approximately how many horsepower is this?

4

_____ do not require any power of force to maintain their field.

Permanent magnets

_____ is also referred to as electromotive force (EMF).

Voltage

_____ were used in vacuum-tube circuits many years ago and are still used today in applications involving field-effect transistors (FETs) and multirange voltmeter circuits.

Voltage dividers

Wire-wound resistors are often used because they are able to operate at _____ power levels than other resistors.

higher

A conductor is made from a material that contains between _____ valence electrons.

one and three

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

opposite

The law of charges states that like charges _____ and opposite charges _____.

repel, attract

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

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 unit of electrical "pressure" that causes current to flow is called the _____.

volt

The Greeks were the first to discover electricity about _____ years ago.

2500

The _____ is used to measure electrical power being used in a circuit.

watt

If a circuit is open, current _____ flow.

will not

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

wire-wound