Physical Science Exam 3: Magnetism & Electrical Power

Name some places the effects of electromagnetism may be seen.

horseshoe magnets, electromagnets, electric motos, compass, transformers, aurora borealis

__________ is a force; the field is _________ near the source & ________ with distance.

Magnetism; strongest; diminishes

Only some substances possess intrisic _______ ______; the most common is ________.

magnetic behavior; iron

Magnetism (like electricity) is _______.

bipolar

Any object that is magnetic has a ________ and a __________ ________.

north; south pole

When a bar magnet is cut in half, you get ____ ______ ________.

2 similar magnets

Magnetism arises out of the arrangment of ___________ in an _________ atom & is intrinsic to that element.

Electrons; iron

___________ are small bundles of atoms sticking together in a magnetic alignment.

domains

Domains in nonmagnetic substances point in _____ ___________ canceling each other’s effect on a nonmagnetic field.

all directions

If a solid is subjected to a strong outside magnetic field, most of the domains will _______ _______ with the external field & the solid becomes a ________.

line up; magnet

______ _______ do not last forever. The ________ will jiggle back into a _____ _______.

bar magnets; domain; random orientation

A ____________ is a small permanent magnet that can rotate about an axis.

compass

___________ completed experiments with magnetism & its relationship to electricity.

Oersted

________ discovered that the lines of a magnetic field generated by an electric current flowing through a wire form _______ ____ about the wire.

Oersted; concentric circles

The field of a magnet held near a wire carrying a current iwll interact with the field _______ __ __________.

generated by current

A stationary electric field does not interact with _____ _______ __________ & no _______ is generated if the electrons move ______ _____ with the magnetic field.

stationary magnetic fields; force; in line

An electromotive force is generated only if a charged particle moves _____ the magnetic field.

across

The magnitude of an electromotive force is proportional to the _____ of the _________ _______ & to the ________ __ ________ passing through it.

strength; magnetic field; amount of current

________ and ___________ independently produced an electric current by moving a magnet up & down through a coil of wire.

Henry; Faraday

________ ________ is generating a current by either moving a magnet perpendicular to a wire or by moving the wire perpendicular to the magnetic field.

Electromagnetic Induction

__________ discovered that the electrical energy can be converted to mechanical work.

Oersted

_______ & _______ discovered that mechanical energy can induce electrical current.

Henry & Faraday

The discoveries of Henry & Faraday paved the way for _________, ________ ______, _________ ________.

electromagnets, electric motors, electric generators

T or F: Permanent magnets are preferred over electromagnets.

False

________ generate magnetic fields from electric currents.

Electromagnets

Coiling a wire in the shape of a loop produces a field the same shape as a ______ _________.

Bar-magnetic field

In an electromagnet the strenght of the field is directly proportional to the _______.

current

___________ is constructed by coiling a wire around iron & connecting the wire coils to a DC source.

electromagnet

________ are more versatile than permanent magnets.

electromagnets

Electric motors were first constructed by __________.

Oersted

Electric motors have only one moving part which is a ______________.

central shaft containing wire coils

In motors, a rotating loop rubs against stationary contacts. This causes the ___________ ________ or __________ to wear out after a while & must be replaced.

rubbing parts; bushings

When a motor is started, a spinning coil does mechanical work & generates electricity. Therefore, every motor is a __________.

generator

________ ________ is the voltage resisting the flow of electrons into a motor.

electromotive force

_________ ________ is the force in a generator opposing an applied mechanical force.

motor effect

List the 4 fundamental physical forces in the universe:

Electromagnetism, gravitation, & 2 forces holding atomic nuclei together

List the inherent properties of matter:

Electromagnetism & gravitation

T or F: All chemical forces are strong & very noticeable.

True

What the charge on a proton?

Positive

What is the charge on an electron?

Negative

__________ travel rapidly if brought near a positively charged particle.

Electrons

T or F? The area around a charge does not affect other charged bodies.

False

If a field is represented by lines: Where the lines are close, the field is _______. Where the lines are father apart, the field is _______. In general, the field of force ________ as you move from the charged body.

intense; weaker; diminishes

Any charged particle whether moving or stationary, generates a ________ ___ ________.

field of force

___________ ______ = constant (charge on A) (charge on B) / (distance between the charges)²

Electrical Force

___________ is the standard unit of charge; equals the charge carried by 6.24×10^18 electrons. MKS system.

Coulomb

_________ is a smaller unit of charge in the CGS system.

Statcoulomb

Electrical charges are __________ or _________.

attractive or repulsive

Like charges ________ one another.

repel

____________ resist the movement of charge in them; do not allow free movement of electrons.

insulators

_________ allow movement of charges in them.

conductors

Give 3 examples of an insulator:

plastic, rubber, air

Give an example of a conductor:

metal

The _________ of a material is a measure of its ability to carry electrical current

conductivity

T or F? There is no such thing as a perfect insulator nor conductor.

True

__________ ______ is a series of pushes in the form of energy.

Electric field

_________ _________ is one directional movement of electrons.

Direct current

______________ _________ current moves one way a small distance, then comes back to the center, then it moves the other way and back to the center again.

Alternating current

______________ in metals carry current.

electrons

___________ in solution carry current.

ions

___________ unit of measurement (MKS) for electrical potential that is measured with respect to some other point.

Volts

___________ is the CGS measurement for electrical potential.

Statvolts

__________ is equal to electric potential times charge.

Energy

________ ________ equals one volt times one coulomb

One joule

_________________ tells us nothing about the movement of the current.

voltage

____________ is a description of the electrical potential of a system.

voltage

___________ is a path or flow of electrical current.

circuit

__________ is the MKS unit for measuring current.

amperes

___________ is the movement of one coulomb of charge past a given point in one second.

ampere

1 amp = 1 __________ = 6.24×10^18 electrons/second

__________ is the CGS unit for current

Stat Amp

See notes for electric symbols for the following:

Battery, Capacitor, Coil, Fuse, Ground, Receptacle, Resistor, Switch, Transformer, AC Source

_________ __________ inhibit the flow of current and cause heat build up.

electrical resistors

__________ is the MKS unit for resistance.

Ohm

_________ is the CGS unit for resistance.

Statohm

___________ are metals cooled to extremely low temperatures (-270 C) causing the resistance to decrease sharply; causes an easy flow of electrons.

Superconductors

_______ get hot.

resistors

___________ the voltage drop across a resistor is equal to the current X resistance or V=IR. Be able to work a problem with Ohm’s law.

Ohm’s Law

________ and ___________ can be converted to heat or work.

electrical and mechanical energy

_______ is generated when an electrical current is passed through a resistor & _________ _____ is generated when an electric current is passed through.

Heat; mechanical work

__________ is energy divided by time.

Power

List the power units:

Watt=1 joule/sec Kilowatt = 1000 watts

________ is current X voltage or IV.

Power

_______ is the push X the amount being pushed around.

Power

A circuit with ________ ___________ carries more current than does a circuit with high resistance.

low resistance

Low resistance allows a high flow of current and causes a __________ _________.

short circuit

Among the wires that come from an outside pole to your house, ______ are hot wired with ________ __________. The third wire is the ________ _________ & is maintained at ________ volts (connected to the ground).

two; alternating current; ground zero;??

Wall sockets operate at ________.

110 volts

Wall sockets are wired with one ________ and one _________ wire.

hot; ground

Some large pieces of equipment & require _________ volts & need both ________ and a ground wire.

220 volts; hot

In a typical house, each wire is wired ________ so when a fuse is blown, there is a short circuit or a broken wire in one area does not affect all areas of the house.

independently

You buy _________ to push electrons around from power companies not the _________ themselves.

energy; electrons

What are 2 types of circuits?

Simple, parallel

Which type of circuit has an advantage in household wiring in that there is always one unbroken wire leading to others from the outlet so one can plug into it while leaving the others vacant.

parallel circuit

In this type of circuit, the disadvantage is that if any outlet along the line is unused, there is a break in the wire & the electricy cannot pass through it.

series circuit

In a ________ _________, the power output of any appliance is dependent upon the other resistors in the line & changes drastically.

series circuit

As you add more resistors to a ______________ circuit, total current decreases.

series

As you add more resistors to a __________ circuit, the total current increases.

parallel

_________ is a device with a metal strip making an electrical connection between 2 points in a wire; it keeps the wire from becoming too hot & causing a fire.

fuse

Good power tools have _________ wires leading from them.

three