electrical homestudy 1

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

270 W, 5%

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

100W, 10%

The effects of electrical force were noticed by the Greeks about ____ how long ago?

2500 years ago

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

3 1/3

An electric motor is running on a 120 V circuit. The current is measured to be 2 amperes. How many ohms of resistance are present in the motor?

60

A precipitator is a type of

Air filter

The strength of an electromagnet is primarily proportional to its

Ampere-turns

A flow of 1 coulomb per second defines

An ampere

The toner in a copy machine sticks to the drum in areas that...

Are charged

Magnetism can be explained by the spinning motion of

Electrons

Resistors which only have one ohmic value called

Fixed resistors

Magnetic lines of force are called

Flux

A semiconductor is normally an atom with ____ (#) electrons in the valance shell.

Four

Matter

Has mass and occupies space

What is Ohm's law:

It takes 1 volt to push 1 ampere through 1 ohm

The lightning damage prevention device that does not connect directly to the object to be protected is called a

Lightning arrestor

A conductor is normally made of atoms with how many electrons in the valence shell

One to three

Which type of magnets do not require any power or force to maintain their field?

Permanent magnets

The atomic number of an element is the number of ____ in the nucleus

Protons

Selenium is a...

Semiconductor

An insulator is normally an atom with ____ (#) electrons in the valance shell

Seven or eight

In a circuit, when the two conductors leading from and back to the power source become connected, this establishes a separate current path that bypasses the load. This is called what?

Short circuit

When electrons are sitting still and not moving, this is referred to as a

Static charge

The manufacture of sandpaper relies on the application of _____

Static electricity

Lightning bolts are a result of...

The discharge of static electricity in thunderclouds

The static charge sometimes used during spray painting is called a

Useful static charge

A resistor made with a wiper arm is called a

Variable resistor

_____ measure the quantity of electrical pressure in a circuit

Voltage

A variable resistor with two terminals is called a

Wire wound resistor

A lightning arrester is used for lightning protection, but is not designed to be struck by lightning itself (lightning rods do). If the protected object is struck by lightning, the high voltage of the lightning _____ across to the lightning arrestor and bleeds to ground

arcs

Like magnetic poles

repel

A 30 ohm resistor is connected to a 4V supply. How many watts will this resistor have to dissipate?

0.533

In an electrical circuit, the voltage is 50 volts and the resistance is 5 watts. What is the value of current?

10 A

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

Wire-wound resistors are often used because they are able to operate at _______ than other resistors

A higher power rating

Electrons in orbit around the nucleus of an atom have magnetic fields. Most of the electrons in most materials pair up in such a way that their magnetic fields ____, leaving the materials nonmagnetic

Cancel

Static electricity is a ____, not a _____

Charge; current

In order to have current flow, the circuit must form a...

Closed loop

What is the term for 6.25 x 10^18 electrons?

Coulomb

Within a lightning bolt, current always flows

From negative to positive

Any time current flow through a resistance, ____ is produced

Heat

The atoms of which three materials form natural magnets?

Iron, nickel, cobalt

Protecting objects from lightning strikes can be done by connecting a conductor from the earth to a piece of metal usually mounted on the roof of a building. The piece of metal is called a...

Lightning rod

The low of charges states that:

Like charges repel and opposite charges attract

The most common method of producing electricity is through the use of

Magnetism

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

Magnetomotive force

The measure of a material's ability to become magnetized is called

Permeability

A variable resistor with a rotating stem and three terminals is called a

Potentiometer

The most accepted theory as to why current flows is

The Electron Flow Theory

Many resistors use ____ to indicate resistance value in ohms and the tolerance of the resistor

Bands of color...interpreted by referring to a "color code"

A magnet that produces a magnetic field as the result of current flow in a conductor is called a(n)

Electromagnet

If a thundercloud has a positive charge, the current in the lightning bolt will in what direction?

From the earth to the cloud

In the Conventional Current Flow Theory, current flows...

From the most positive point to the most negative point

A variable resistor with a shaft that rotates more than one rotation is called a

Multiturn variable resistor

The part of an atom that has no charge

Neutron

The nucleus of an atom contains

Neutrons and protons

Using a pre-charged electroscope, when a charged test object is brought near the ball, the leaves move closer together. This indicates that the test object charge is the _____ polarity as the electroscope charge

Opposite

Valence electrons are contained in the ____ shell

Outermost

Voltage does not flow, but is the "_____" that makes ____flow

Pressure; current

The measure of a material's resistance to being magnetized is called

Reluctance

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

Selenium

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

Variable resistor

There are two types of electrical sources:

DC, AC

Connecting a 150 ohm, ½-W resistor to a 9v power supply will ____

Damage the resistor

Current that flows in only one direction is referred to as

Direct current

Short circuits generally cause a ____ to blow, or a ____ to open

Fuse; circuit breaker

The regions formed in the molecular structure of magnetic metals by electrons which spin in the same direction, causing their magnetic fields to add instead of cancel, are called...

Magnetic domains

A thundercloud can obtain ____ and ____ charges

Positive and negative

When resistors are manufactured, the processes are not perfectly exact. Each resistor may be slightly different from the next one. The plus and minus limits of a resistor's ohmic value is called

Tolerance