Physics: Electricity & Magnetism

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Electric field strength equation

E= F on q/q

Total energy to be converted to thermal energy can be written as

E=pt E= O^2Rt E= (v^2/r)t

Work=

F (force) D (direction

Coulomb's Law

F = k • Q1 • Q2 / d2

eddy current

Generated in the metal and produce a magnetic field that acts to oppose the motion that caused the currents

Volt

Measure of V. It is J/C

Are individual charges created?

No, Individual charges are never created or destroyed, they are just transferred

E=? (KWH)

PxT (KWxHours)

Coulomb (C)

The Si unit of charge

What happens to the current if the amount of charge increases?

The current increases as well

Electric current

The flow of charges

Resistance (R).

The measure of how strongly an object or a material impedes current produced by a potential difference.

electromagnetic induction

The process of generating a current through a circuit

Power

The work done in an amount of time

What three physical properties affect the resistance in a wire?

Thickness/thinness, Longer/shorter, or the type of material.

Ampere

Unit for current

equipotential.

When the electric potential difference between two or more positions is 0, the positions are called

What are the units for power?

Work (W)

A galvanometer indicates

a flow of electrons.

third right-hand rule

a method that can be used to determine the direction of the force on a current-carrying wire in a magnetic field

second right-hand rule

a method used to determine the direction of the field produced by an electromagnet, relative to the flow of conventional current

Gravitational forces

are always attractive.

Like kinds of magnetic poles repel while unlike kinds of magnetic poles

attract

Electrostatic forces

can be either repulsive or attractive,

Whereas electric charges can be isolated, magnetic poles

cannot

a battery

converts chemical energy to electrical energy

The resistance for most conductors __________ as the magnitude or direction of the potential difference applied to it changes.

does not vary

Any charge paces in an electric field experiences a force on it resulting from the ___________ at that location.

electric field

Over geologic history the Earth's magnetic field

has reversed direction many times.

Neutral atoms

have the same amount of positive and negative charges.

Electroscope

helps to determine charge. It is a metal knob connected by a metal stem to two thin, lightweight pieces of metal foil called leaves that are enclosed to eliminate air currents.

Positive charges flow from a ________ potential to a ________ potential

higher, lower

If the electric potential difference between the plates increases, the amount of charge on each place _______.

increases

Resistance ____________ as the cross sectional area decreases

increases

Resistance increases as length __________

increases

Magnetic domains normally occur in

iron

Electoral potential (voltage)

is electric potential energy per unit charge.

Like charges

like charges always repel

Coulomb's law only gives _________, not ___________.

magnitude, direction

Magnetism is due to the motion of electrons as they

move around the nucleus. spin on their axes.

The source of all magnetism is

moving electric charge.

if the charged rod is removed before the ground is broke, the sphere is ___________

neutral again

electrical resistance increases with...

-increasing wire length -increasing temperature -decreasing wire thickness

If a 9V battery exits at positive and connects at negative with a 7V battery, what is the final voltage?

16V

Electric circuit

A closed system or a path in which electrons from a voltage or current source flow

Capacitor

A small device for storing electric energy.

transformer

A transformer has two coils wound about the same core. An AC current through the primary coil induces an alternating EMF in the secondary coil. The voltages in alternating-current circuits may be increased or decreased by transformers.

What are the units for current?

Amps

What is ammeter?

An ammeter measures amps (current)

electrical resistance decreases with...

-decreasing wire length -decreasing temperature -increasing wire thickness

Larger the charge or distance moved...

...the greater the increase in the electric potential energy.

Elementary charge is equal to...

1.602 x 10^-19

A kilowatt-hour is equal to

1000 watts delivered continuously for an hour (3600 seconds). It is a unit of energy

To be able to find the voltage of two battery's, you must read what signs the battery's link together with. If a 6V battery exits at positive and connects at positive with a 3V battery, what is the final voltage?

3V

What is the resistance and range of a resistor with the colors, Yellow, Violet, Black, Gold?

47 ohms, and +- 2.35

One C is equal to...

6.24 x 10^18 electrons or protons.

the constant (K) in coulomb's law is equal to...

9.0 x 10^9

potentiometer

A device that can be used to change the current in a circuit in a continuous way

circuit schematic.

A diagram with symbols

Schematic

A drawing of a circuit using symbols

What is a voltmeter?

A voltmeter measures volts (voltage)

Series Circuit

An electric circuit in which electrical devices are connected along a single path. -the current that goes through each resistor is the same -the total resistance in the circuit is the sum of the resistances of each item in the circuit -the current in the circuit is given by Ohm's Law (voltage is supplied by battery, resistance is sum of each item) -voltage will drop across each device (total voltage drop will equal voyage supplied by battery)

equivalent resistance

the value of a single resistor that could replace all resistors in a circuit without changing the current

Parallel Circuit

An electric circuit in which electrical devices are connected along parallel paths -the voltage across each parallel path is the same -Ohm's Law applies to each branch -the total current is equal to the current through each individual path -the resistance decreases as the # of paths increases

electric circuit.

Any closed loop or conducting path allowing electric charges to flow

What is the color table?

Black 0 Brown 1 Red 2 Orange 3 Yellow 4 Green 5 Blue 6 Violet 7 Gray 8 White 9

Charging by induction

Charging a neutral object by bringing a charges object near

Charging by conduction

Charging a neutral object by touching that object with a charged object

Ohm's Law

Describes the relationship between current, resistance, and voltage: I=V/R amperes=volts/ohms

Types of Current

Direct Current (DC) , Alternating Current (AC)

One equation for energy

E= q change in V.

Solar winds headed in Earth's direction are deviated mainly by

Earth's magnetic field.

electrical pumps

Electrical pumps separate positive charges from negative charges (ex. battery or generator)

Direct Current (DC)

Electrically charged particles flowing in only one direction. (type of current set up in a simple current)

Alternating Current (AC)

Electrically charged particles the flow in alternating directions. (type of current in households)

Work on q=

FD

Field vectors

Field vectors Make a model of an electric field by using arrows to represent the field vectors at various locations Length of an arrow represents field strength in vectors.

ampere (A).

Flow of electric charge equal to one coulomb per second.

What colors are always at the bottom of the resistor? How do you find their range?

Gold and silver, gold multiply the resistance by 5% (0.05) for silver multiply the resistance by 10% (0.1) *don't forget all answers are + or -!!!!!*

(optional equation) P=? (Power)

I^2xR (Current squared multiplied by Resistance)

electric generator

Invented by Michael Faraday, converts mechanical energy to electrical energy. Consists of a number of wire loops placed in a strong magnetic field.

V=? (Voltage)

IxR (Current multiplied by resistance)

P=? (Power)

IxV (Current multiplied by Voltage)

Lenz's law

Lenz's law states that an induced current is always produced in a direction such that the magnetic field resulting from the induced current opposes the change in the magnetic field that is causing the induced current.

Newtons/Coulomb

Magnitude of the electric field is measured in this.

Battery

Maintains voltage by circuit, chemical --> electric

Anmeter

Measures current. It is connected in series with the part of the circuit it measures. (has very low internal resistances)

Voltmeter

Measures potential difference/voltage. It is connected in parallel with the circuit element that is measured. (has very high internal resistances)

electrical resistance

Measures the amount a material resists an electric current. Measured in Ohms (omega)

How do you convert 3 Watts to KW?

Move the decimal three to the left, .003 KW.

Electric field lines are directed towards _________

Negative charges.

What are the units for resistance?

Ohms (Ω)

Resistence

Opposition to the flow, slows down electrons

self-inductance

Self-inductance is a property of a wire carrying a changing current. The faster the current is changing, the greater the induced EMF that opposes that change.

Types of Circuits

Series Circuit, Parallel Circuit

Battery

Several galvanic cells connected together

Capacitance

Slope of the line in a net charge versus potential difference graph is a constant and called the _______ of a capacitor. You can measure the it in farads (F) where 1 F= I C/V.

mutual inductance

The changing field induces a varying EMF.

What happens to the current if the time increases?

The current will decrease

potential difference

The difference in electric potential between two points, measured in volts (V). (also known as voltage difference)

electric current

The flow of electric charge that transports energy from one place to another. In order for current to flow through a circuit, a voltage difference must be maintained. Measured in amperes (A).

Elementary charge

The magnitude of charge of a single electron or proton

Resistor

The object to the opposition of flow of electric charge

electromotive force (EMF)

The potential difference, or voltage, given to the charges by a battery

average power

The power produced by a generator is the product of the current and the voltage

Current can be changed by varying _________ or both.

V,R

How do power companies reduce the amount of energy lost to hear when transmitting electricity?

With low resistance and a high voltage

Do charges exert forces on each other?

Yes, separated positive and negative charges exert forces on one another

A plasma sphere's central electrode is...

a charged object whose net charge alternates rapidly between positive net charge and negative net charge.

parallel circuit

a circuit in which there are several different paths for a current

series circuit

a circuit in which there is only one current path

combination series-parallel circuit

a circuit that has some branches in parallel and some in series

ground-fault interrupter

a device that detects small differences in current caused by an extra current path and opens the circuit

galvanometer

a device that is used to measure very small currents can be used as a voltmeter or an ammeter

ammeter

a device used to measure the current in part of a circuit

voltmeter

a device used to measure the potential difference between two points

Charges exert forces on other charges at _________

a distance

electric current

a flow of charged particles

solenoid

a long coil of wire with many loops; fields from each loop add to the fields of the other loops, creating a greater total field strength

electromagnet

a magnet created when current flows through a wire coil

Surrounding every moving electron and stationary electron is

a magnetic field. an electric field.

Conductor

a material that allows charges to move easily (charge will spread out).

first right-hand rule

a method used to determine the direction of a magnetic field relative to the direction of conventional current

When current reverses direction in a wire, the surrounding magnetic field

also reverses direction.

electric motor

an apparatus that converts mechanical energy to electric energy and consists of a number of wire loops placed in a strong magnetic field

circuit breaker

an automatic switch that opens a circuit when the current reaches some set value, stopping electric charge flow

Surrounding every magnet is

an electric field. a magnetic field.

A current-carrying coil of wire is

an electromagnet.

When charges flow through the device that reduces electric potential energy, the energy is transformed into _____________

another kind of energy

An electric field exists when?

around any charged object. The field produces forces on other charged objects.

Electric potential difference increases as you pull a

as you pull a positive test charge away from a negative charge.

The direction of the force exerted on a moving charge in a magnetic field is

at right angles to the direction of the motion.

Positive atoms

atoms that are missing electrons

Negative atoms

atoms that have gained electrons

When a current-carrying wire is bent into a loop, its magnetic field inside the loop

becomes concentrated.

How do you produce a uniform electric field?

by placing two large flat conducting plates parallel to each other.

Van de graaff generators

can build up a large amount of net charge on its metal dome. When a person touches the metal dome, the positively charged dome attracts the electrons in the person's body. Their hair becomes positively charged and the individual hairs repel each other.

In the atoms of most materials the fields of individual electrons

cancel one another.

Electric potential difference in a uniform field equation

change in V= Ed

Magnetic field lines about a current-carrying wire

circle the wire in closed loops.

The number of electrons in a __________ does not change

closed circuit

Magnetic field strength about a magnet is strongest where magnetic field lines are

closer together

The field is stronger when the lines are _________

closer together

The force is stronger when the charges are __________

closer together

Generator

converts mechanical energy to electrical energy

a generator

converts mechanical energy to electrical energy

a solar cell

converts radiant energy to electrical energy

Potential energy ________ as you move the two charges further apart.

decreases

the electric potential _________ when a positive charge is moved towards a negative charge

decreases

polarized

describes the property of having two distinct, opposite ends, one of which is a north-seeking pole and the other of which is a south-seeking pole

a lamp

designed to convert electrical energy to radiant energy

only ________ in electric potential can be measured

differences

When an electron passes through the magnetic field of a horseshoe magnet, the electron's

direction is changed.

Ohm's law states that the current through a wire is _______________ to the potential difference between its ends.

directly proportional

JJ Thomson

discovered that all materials contain electrons

Ernest Rutherford

discovered that the atom has a massive positively charged nucleus surrounded by a cloud of orbiting electrons.

To weaken a bar magnet

drop it on a hard surface. put it in hot flames. whack it with a hammer.

If the connection to the ground is broken before the charged rod is removed, the sphere is ______________

either positively or negatively charged

A galvanometer can be calibrated to measure

electric current. electric voltage.

a motor

electric energy to mechanical energy

Which force field can increase a moving electron's speed?

electric field

Which force field can accelerate an electron?

electric field magnetic field

The work performed moving a charged particle in an electric field can result in the particle gaining _________ energy, __________ energy, or both.

electric potential, kinetic

Power is the rate at which

energy is transferred or transformed.

Compared to the huge force that attracts an iron tack to a strong magnet, the force that the tack exerts on the magnet is

equally huge.

Magnet A has twice the magnetic field strength of Magnet B and at a certain distance pulls on magnet B with a force of 100 N. The amount of force that magnet A exerts on magnet B is

exactly 100 N.

The field is weaker when the lines are __________

farther apart.

fourth right-hand rule

find the force on the charges in the wire hold your right hand so that your thumb points in the direction in which the wire is moving and your fingers point in the direction of the magnetic field. The palm of your hand will point in the direction of the conventional (positive) current

Coulomb's law is only valid...

for point charges or for charges that are spread uniformly over a sphere.

An aurora borealis high above the atmosphere is due to

fountains of high-speed charged particles, trapping of charged particles by Earth's magnetic field, disturbances in Earth's magnetic field. (ALL OF THE ABOVE)

examples of insulators

glass, dry wood, plastics, cloth, and dry air

A compass is moved from the Northern Hemisphere to the Southern Hemisphere. Assume that the only magnetic field that acts on the compass is the Earth's magnetic field, and that this field is the same as the field of a dipole with the locations of the poles described in the textbook. When the compass is moved through the equator, the magnetic needle of the compass will change direction relative to the meridian

hardly at all.

If you break a bar magnet in half you'll

have two magnets

Place an iron rod inside a current-carrying coil of wire and you

increase the strength of the electromagnet.

The ___________ in potential difference by the generator equals the __________ in potential difference by the motor.

increase, decrease

Resistance usually increases as temperature ____________

increases

Total resistance ____________ with the length of wire

increases

Work _________ the electric potential energy of a two charge system.

increases

Higher capacitance is obtained by __________ the surface area and ____________ the separation of the plates.

increasing, decreasing

A resistor

is a device designed to have a specific resistance.

Insulator

is a material in which a charge will not move easily. (charge will stay in place)

electric field

is a property of the space around a charged object that exerts forces on other charged objects.

What does the electric potential difference depend on?

it does not depend on the magnitude of the test charge, it only depends on the field and the displacement.

The amount of energy used by a device is

its rate of energy consumption in joules per second, or watts, multiplied by the number of seconds the device is operated.

The purpose of increasing the potential difference when transmitting electrical energy over long distances is to decrease __________________.

joule heating loss

in the transmission of electrical energy, some power is lost to thermal energy. Electrical engineers call this unwanted thermal energy the _________

joule heating loss

Wood does not have magnetic properties because it contains no

magnetic domains.

Into which stable force field can a proton be placed at rest without being acted upon by a force?

magnetic field

The force that acts between a pair of magnetic poles depends on

magnetic pole strength. separation distance.

Pigeons navigate primarily by

magnetic sensors in their heads.

A current-carrying wire in a magnetic field

may be deflected. may experience a force.

An electron beam directed through a magnetic field

may experience a force. may be deflected.

A compass needle in a magnetic field

may experience a pair of torques.

examples of conductors

metals, plasma, graphite, air momentarily with lightning is involved.

Net charge can only be a _____ of e, not a _____ of e.

multiple, fraction.

Hard rubber and plastic have a tendency to become ________________

negatively charged

A superconductor is a material with ________ resistance

no

No net force acts on a loop of wire in a magnetic field when

no current is in the loop. no magnetic field lines pass through the loop.

A current-carrying loop of wire experiences no tendency to rotate in a magnetic field when

no field lines pass through the loop.

The flow continues until there is ______________ between the spheres

no potential difference

Several paper clips dangle from the north pole of a magnet. The induced pole in the bottom of the lowermost paper clip is a

north pole.

The end of a compass needle that points to the south pole of a magnet is the

north pole.

The conventional direction of magnetic field lines outside a magnet are from

north to south.

A device having constant resistance independent of the potential difference ______________

obeys ohm's law

Resistance is measured in

ohms.

The energy carried by an electric current depends

on the charge transferred and the potential difference across which it moves.

primary coil

one coil

The flow of electrons and the direction of conventional current are in __________ directions

opposite

the potential increases in the direction _______ the electric field direction

opposite

secondary coil

other coil

Cosmic rays penetrate your body when

outdoors. in mountainous regions. safely in your home.

Always associate the words "voltage across" with a ____________ connection

parallel

Any time the current has two or more paths to follow in a circuit, the connection is a __________ connection

parallel

A beam of electrons can pass through a magnetic field without being deflected if the direction of the beam is

parallel to the field lines.

A beam of electrons passing through a magnetic field experiences maximum deflection if the direction of the beam is

perpendicular to the field lines.

The force a magnetic field exerts on a current-carrying wire is maximum when the wire is oriented

perpendicular to the magnetic field.

The force exerted on an electron moving in a magnetic field is maximum when the electron moves

perpendicular to the magnetic field.

A connection with one current path in a circuit is a __________ connection

series

Always associate the words "current through" with a _________ connection.

series

Refrigerator magnets are typically

short range

conventional current

the direction in which a positive test charge moves

electric field lines

the lines providing a picture of the size and strength of the field around a charged object.

An iron rod becomes magnetic when

the net spins of many of its electrons are aligned.

magnetic flux

the number of magnetic field lines that pass through a surface

short circuit

the occurrence when a circuit forms that has a very low resistance

Electric Power

the rate of energy transfer, or rate of work, or the amount of energy per unit of time: power= current x voltage (measured in watts (W))

The force on an electron moving in a magnetic field will be least when its direction is

the same as the magnetic field direction.

The current is ____ a series circuit.

the same everywhere

step-up transformer

the secondary voltage is larger than the primary voltage

The closer charges are to each other,

the stronger the electrostatic force between them.

Electrostatics

the study of electric charges/ the study of static electricity

step-down transformer

the voltage coming out of the transformer is smaller than the voltage put in

armature

the wire could of an electric motor, made up of many loops mounted on an axle of shaft; torque on an armature, an the motor's resultant speed, is controlled by varying the current through the motor

Application of Electrostatic Forces:

there are many commercial and industrial applications of electrostatic forces. Tiny paint droplets are charged by induction. Photo copies. Laser printers.

The total charge passing through a point on a circuit is the current multiplied by the _______ the charge flows

time

Force is directly proportional...

to the strength of the test charge.

Unlike charges

unlike charges always attract

(optional equation) P=? (Power)

v^2/R (Voltage squared divided by resistance)

Electrostatic force is a _________, it has magnitude and direction.

vector

Power is measured in

watts (W).

Force varies directly

with the charge on the body.

Magnitude of electric force varies inversely

with the square of the distances between the center of the spheres.

How do you determine direction of electrostatic force?

you can determine direction by drawing a diagram of force vectors and applying vector addition.

Electric potential difference (V)=

ΔV=work on q/q. (the work done moving a positive test charge between two points in an electric field divided by the magnitude of the test charge).

I=? (Current)

Q/T (Charge divided by Time)

Equation for Resistance.

R= V/I (potential difference divided by current)

What is the purpose of a generator?

Creates electrical energy, and converts mechanical energy into electrical energy

Which way does conventional current flow?

Positive ---> negative

What are the two different types of charges

Positive and negative

Three Equations for Power.

Power is equal to the current times the potential difference. (P=IV) Power is equal to = i^2R Power is also equal to= V^2/R

Which is greater, the speed of an electron traveling through a wire, or the speed of light?

The speed of light

voltage divider

a series circuit used to produce a voltage source from a higher-voltage battery

fuse

a short piece of metal that melts if a current that is too large passes through it

domain

a very small group, usually 10-1000 u, that is formed when the magnetic fields of the electrons in a group of neighboring atoms are aligned in the same direction

The magnetic fields of a pair of nearby magnets can

add or subtract by vector rules.

Magnetic fields are produced by

all moving electrical charges.

An ammeter measures

current

The intensity of cosmic rays bombarding the Earth's surface is most at the

poles

glass and wool have a tendency to become ____________.

positively charged

The EPD is higher near the ________ charged plate and lower in the ________ charged plate.

positively, negatively

There is no _____________ across a superconducting wire

potential difference

A voltmeter measures

potential differences

If a magnet produces a force on a current-carrying wire, the wire

produces a force on the magnet.

Earth's magnetic field is

protective to life on Earth.

C=

q/ change in V.

Grounding

removing excess charge by connecting an object to earth.

When you pull a + charge from a + charge, there is a _____________ force between the two.

repulsive

Although a magnet can change the direction of travel of an electron beam, it cannot change its

speed kinetic energy.

Electric potential difference does not depend on the path used to go from one position to another. It depends only on the _________ positions on that path.

starting and final

Electrostatic forces are typically ________ than gravitational forces.

stronger

In an electric circuit, the potential difference provided by the generator or other energy source, Vsource, is equal to the ____ of drops in electric potential across the resistors.

sum

A superconducting magnet uses

superconducting coils.

magnetic fields

the area around a magnet, or around any current-carrying wire or coil of wire, where a magnetic force exists


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