Science Test Electric Fields, Potential, Elctrostatics, Coloumb's Law, Voltage

How do you shield an electric field?

-Surround you object in a conducting surface -put surface in an electric field of whatever strength - the free charges in the conducting surface will arrange themselves on the surface of the conductor in a way such that all field contribution inside cancel one another.

K

9 x 10^9 (N)(M)^2/ C^2

Energy between parallel plates

Energy between parallel plates is uniform

lines when there are 2 are more opposite charges and when there is an isolated charge

For an isolated charge, the lines extend to infinity For two or more opposite charges, the lines emenate from a positive charge and terminate of a negative charge

Electrical potential energy

The energy a charge has due to its location in an electric field. Unit is joules i.e. 2 charges in the same location will have twice the electrical potential energy EPE= fd or EPE= vq

What charge are protons?

Protons are positively charged. More protons than electrons= positive charge. Less protons than electrons= negative charge

When is the electrical potential energy of a charged partical increased?

The electrical potential energy of a charged partical is increased when work is done to push it against the electric field of something else that is charged. Similar to when work is done to lift an object against Earths gravitational field. The small positive charge has more potential enrgy when it is closer to the positivly charged sphere because work is required to move it to the closer location.

Electrical forces

arise from particles in atoms. The protons in the nucleas attract the electrons and hold them in orbit. Electrons are attracted to protons but electrons repel other electrons.

Semiconductors

materials that can be made to behave sometimes as insulators and sometimes as conductors. Atoms in a semiconductor hold their electrons until given small energy boosts.

Van de graff generator

moving rubberbelt carries electrons from the voltage source to a conducting sphere. These devices accelerate charged particals used as projectiles for penetrating the nuclei of atoms

q

quantity of charge (charge symbol)

coulombs law

relationship between electrical forces, charges and distance. Discovered by French Physist Charles Coulombin 18thcentury States that for charged particals or objects that are small compared with the distance between them the force between the charges varies directly as the product of the charges and inversly as the square of the distance between them. F= k q1q2/d^2

coulomb

unit of charge abrreviated c. A charge of 1c= 6.25 billion or 6.24 x 10^18 electrons

transistor

used in indigital media players. Layers of semiconducting materials sandwiched together. They amplify electric signals and control currents in circuits with very little power.

grounding

when we allow charges to move off (or onto) a conductor by touching it

What makes a neutral atom?

A neutral atom is made when there are as many protns as electrons

When can charge polarization occur?

Charge polarization can occur in insulators that are near a charged object

What can be described as theinteraction between one charge and the electric field set up by it?

The force that one electric charge exerts on another can be described as the interaction between one charge and the electric field set up by it.

electrostatics

electricity at rest. Involves elctric charges, forces between them and their behaivor in materials

An object can be electrically charged in 3 ways

1. By friction when electrons are transferred from one object to another by friction 2. By contact when electrons are transferred from one object to another by direct contact without rubbing 3. By induction when electrons are caused to gather or disperse by the presence of a near by charge ( even without physical contact). The result is a redistrobution of a charge on an object without any change in its net charge. If the object is an insulator there is a realignment rather than a migration of charge occurs. Polarization in which the surface near the charged object becomes oppositly charged. i.e. Balloon to wall

Rules for electric field lines

1. Starts on positive or infinity 2. Ends on negative or infinity 3. perpendicular to the charged surface

the force of repulsion between two charges 1c each 1m apart

1c each 1m apart the force of repulsion between two charges would be 9billion newtons

Electrically charged

An object that has an unequal number of electrons and protons

Voltage

Another name for volt. Zero voltage has been specified a definite value for it can be assigned to a location wether or not a charge exists at the location. We can speak about voltages at different locations in an electric field wehter or not there is a charge in those locations

Atoms + Nucleas

Atoms have positively charged nucleas surrounded by negatively charged electrons. All electrons are identical: each ahs the same mass and same quantity of negative charge as every other electron. Nucleas compsed of protons + neutrons ( except hydrogen has no neutrons) All protons= identical. Proton has 2000 times the mass of electrons but positivly charged, and equal in magnitude to the negative charge of an electron. Neutron has no charge + slightly bigger than a proton

ELectric field stength formula

E= F/q The force on a charged partical gives the electric field strength

What is always a whole number?

ELectrons are always whole number cannot be divied into fractions

Electric potential

EP= electrical potential energy/ charge Unit of EP is volt V= EPE/ q 1volt= 1 joule/ 1 coulombs

Electrons movement in conductors and insulators

Electrons can move easily in good conductors and poorly in good insulators

What charge do electrons have?

Electrons have a negative charge. Gain electrons= negeative charge. Loose electrons= Positive charge

When do electron settle down or/and stop moving? Absence of an electric field inside a conductor?

Free electrons within a conductor settle down and/or stop moving only when the electric field is zero. So the charges arrange themselves to ensure a zero field within the material.

Greatest difference between gravitational and electric forces

Greatest difference between gravitational and electric forces is that while gravity only attracts, electrical forces either attract or repel

What depends on how much energy it takes to tear an electron away from an atom?

How much energy is required to tear an electron way from and atom varies for different substances. i.e. electrons held more firmly in rubber band than in fur.

What will happen to the electrons if a charged object is brought near a conducting surface, without physical contact?

If a charged object is brought near a conducting surface even without physical contact electrons will move in the conducting surface.

If the charge on a conductor is not moving, what is the electic field inside the conductor?

If the charge on a conductor is not moving, the electic field inside the conductor is exactly zero.

Induction

Induction is the charging of an object without direct contact

Fundemental rule at the base of all electrical phenomena

Like charges repel and opposite charges attract

Conductors

Materials through which electric charge can flow

What charge or neutrons?

Neutrons have no charge and are neither attracted nor repelled by charged particles

Electrically Polarized

One side of the atom or molecule is induced to be slightly more posotive or negative than the opposite side.

Insulators

Poor conductors of electricity and heat

Chargeing by friction and contact examples

Scuff shoes against the floor touch the doorknob = shock= friction= electric charge Charged rod placed in contact with a neutral object= some charge transfers to the neutral object= charging through contact

Direction of an electric field at any point

The direction of an electric field at any point by convention (convention= away in which things are normally done/ meeting with a group of people), is the direction of the electrical force on a small positive test charge placed at that point. - Negative charge = field points toward the charge - Positive charge = field points away from the charge

What does the energy stored in a capacitor come from?

The energy stored in a capacitor comes from the work done to charge it. The energy is in the form of the electric field between its plates so the energy is stored in a capacitor is energy stored in the electric field

How do you get your electric field to zero?

The exact charge distrobution over the surface is such that the electric field everywhere inside the cunductor is zero. Electrons on the left lide side of the sphere would tend to pull the test charge to the left but the electrons on the right side of the sphere would tend to pull the test charge to the right equally hard, this means the net force on the test charge is zero which means the electric field is zero

How is the strength of an electric field measured

The magnitude (strength) of an electric field can be measured by its effect on charges located in the field . i.e. small posotive test charge placed in an electric field. Where the force is greatest on the test charge the field is strongest. Where the force on the test charge is weak, the field is small

Bonding

The negative electrons of one atom may at times be closer to the neighboring atom's positive nucleas than they are to the average location of the neighbor's electrons. Then the attractive force between these charges is greater than the repulsive force. Bonding also leads to the formation of molecules

Conservation of charge

The principle that electrons are neither created not destroyed but are simply transferred.

How can the voltage of a Van de Graff generator can be increased?

The voltage of a Van de Graff generator can be increased by increasing the radius of the sphere or by placing the entire system in a container filled with high pressure gas.

What are two ways electric charge be transferred?

Two ways electric charge can be transferred are by friction and by contact.

volatage capacitor formula

V = Ed

Electric Dipoles

When molecules normal states are electrically porlarized. The distrobution of electrically charge is not perfectly even

Induced

When the charge has been redistributed or induced

What happens to your charge when you have a conductor that is not spherical?

When your conductor is not spherical the charge distrobution will not be uniform

What is work equal to?

Work is equal to the energy gained by the charge

Electric field lines

You can use electric field lines (also called lines of force) to represent an electric field. Where the lines are farther apart, the field is greater. Length of vectors indicates the magnitude of the field

ion

a charged atom. Positive ion/ Negative ion

Electric field

a force field that surrounds an electric charge or group of charges. Has magnitude and direction so is a vector. Electric fields are store houses of energy

gravitational field

a forcefield that surrounds a mass

capacitor

electrical energy can be stored in this device. Capasitors store and hold electric charges until discharged. A charged capacitor is discharged when a conducting path is provided between the plates. Capacitors might store charge even after the electricity to a device has been turned off- for seconds/minutes or longer The

electrical potential energy per charge at any location...

electrical potential energy per charge at any location, no matter that amount of charge, will be the same

Volt

symbol is V. Named after the italian physist Allesandro Volta

Charge

the fundemental electrical property to which the mutual attractions or repulsions between electrons or protons is attributed