General Physics 2 Midterm Test

ATOMS

Composed of particles with different charges: neutrons, protons ,(+C) , and electrons (-C)

Electric Charge

Electric charges are usually represented by q.

The SI unit of charge is the coulomb (C).

Elementary Charge

Represented by e. It is the electric charge carried by a single proton.

proton

has a charge of + e

electron

 has a charge of **– e**.

Coulombs

unit of electric charge

1\.602x10^-19 C

Coulomb’s constant

Conductivity

Measure of the ease at which an electric charge moves through a material.

Conductors

Materials that readily allow the flow of charges. Metals are good ___ since they have plenty of free electrons that can easily move in a material.

Insulators

Materials that resist the flow of charges. Examples: rubber, plastic, mica, paper, glass, & air.

Semiconductors

Intermediate between conductors & insulators. Examples: silicon, germanium and gallium arsenide. In pure form, ___ have low conductivity. Through the process of doping, atoms of various elements are added in small amounts to semiconductors to increase conductivity. ADDING to a conductor = increase conductivity

Superconductors

A material that has practically no resistance to the flow of charges. a substance, especially a metal, that allows an electrical current to move freely through it at a very low temperature. magnets

Friction

* Results when two __different__ materials are rubbed together.
* There is contact
* One material will have a **positive** charge, while the other **negative**.
* Loses electrons (positive, stands), Gains electrons (negative)

Conduction

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* Requires __physical contact__ between a charging (source) body & a neutral body.
* A neutral body will transfer electrons to a positive body. 
* Ex. positive body = outlet
* A negative body will transfer electrons to a neutral body.

Induction

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* The process wherein a __nearby__ neutral body is charged __without physical contact__ by a charged body. 
* Ex. wireless charging
* The negative charges on the neutral body are attracted toward the charging body if the latter is positive. 
* They are repelled from the charging body if it is negatively charged.  
* This effect is known as __polarization__.  
* Earth is a reservoir of charges. 
* Electrons from a neutral body will travel down the ground if the charging body is negative. 
* Electrons will travel up the ground connection to the neutral body if the charging body is positive. 

Principle of Conservation of Charge

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* Total charge of an isolated system remains constant.
* Charges cannot be created nor destroyed. 
* In any charging process, charges are merely __transferred__ from one body to another. 

Coulomb’s Law

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* The magnitude of electrical force between two charged particles is __directly__ proportional to the product of the magnitude of their charges and __inversely__ proportional to the square of the distance between them.

Superposition Principle

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* three or more
* Each charge will exert a force on another charge as if no other charges are present. 
* The total force that a particular charge experiences due to a collection of charges is the __vector sum__ of all individual forces.

Electric force

 is a noncontact force

ELECTRIC FIELD

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* The space surrounding a charged body
* cause any charged particle placed in it to experience an electric force.
* exists in the region of space around a charged object or a source charge

positively and negatively

Lines of force start from ___ charged particles and end on _ charged particles.

stronger

The greater number of lines of force, the __ the field.

ELECTRIC FIELD INTENSITY

The strength of the electric field at a point due to the source charge

positive

Physicists use a unit ___ charge as the test charge in defining an electric field. This test charge and the electric field are usually represented by qo and E respectively.

VOLTAGE

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* the charge (electron) “pusher.” 
* causes current to flow/move.

Volts

Unit for voltage

Alessandro Volta

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* Italian physicist 
* known especially for the invention of the electrochemical cell, aka the battery in 1800.

CURRENT

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* flow of charge (electrons) within a conductor or how fast charge is moving.
* Charge will only flow if there is a voltage source (potential difference).  

Amps

Unit for Current

Andre Ampere

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* French physicist and mathematician. 
* One of the main discoverers of electromagnetism.
* SI unit of measurement of electric current, the ampere, is named after him.

RESISTANCE

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* opposes the push from the voltage source.
* affects the speed of the current.

Ohms

Unit for Resistance

Georg Ohm

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* German physicist
* determined that there is a direct proportionality between the voltage applied across a conductor and the electric current.

directly

Length and resistance are ___ proportional

inversely

CROSS-SECTIONAL AREA and resistance are ___ proportional

directly

Temperature and resistance are ___ proportional

OHM’S LAW

State the relationship between current, voltage, and resistance.

V=IR

Formula of Ohm’s Law

directly

voltage and current are __ proportional

inversely

Resistance and Current are __ proportional

directly

Voltage and Resistance are __ proportional

Electric Power

The rate at which a device changes electric current to another form of energy

watt

SI unit for power

Power = current x voltage

formula for electric power

Resistor

A passive two-terminal electrical component that implements electrical resistance as a circuit element. 

In electronic circuits, ___ are used to reduce current flow and to divide voltages.

Battery

Is a device that __stores__ energy and makes it available in an electrical form.

Converts chemical energy into electrical energy or vice versa

Switch

An electrical component that can __break__ an electric circuit, interrupting the current or diverting it from one conductor to another.

emboss

the positive side is in which side of a battery

flat

the negative side is in which side of a battery

Short Circuit

malfunction

Series Circuit

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* Each device occurs one after the other sequentially.
* The Christmas light dilemma: If one light goes out all of them go out.
* Electrons only have one path to flow through

Parallel Circuit

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* exists where components are connected across the same voltage source.
* are similar to those used in homes.
* There are multiple paths for the current to flow through

LOOPS

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* each + all
* any closed path going through circuit elements.

NODES

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* intersection of wire between other wires
* any region on a circuit between two circuit elements

Loop Rule

The sum of the potential drops (Resistors) equals the sum of the potential rises (Battery or cell) around a closed loop.

(Conservation of Energy)

Kirchhoff's Voltage Law (KVL)

Junction Rule

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* The sum of the magnitudes of the currents going into a junction equals the sum of the magnitudes of the currents leaving a junction.
* IN = OUT (current)
* (Conservation of Electric Charge)
* Kirchhoff's Current Law (KCL)

\+E

VOLTAGE: coming out of positive

\-E

VOLTAGE: coming out of negative

\-IR

Current and Resistance: same direction

\+IR

Current and Resistance: different direction

Magnetism

ability of magnetic material to attract/repel other magnetic materials.

MAGNETS

materials that are able to attract other magnetic materials

MAGNETIC MATERIALS

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* materials that are attracted to a magnet. (i.e. iron, nickel, cobalt and some alloys)

ARTIFICIAL MAGNETS

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* can be made using magnetic materials. 
* Anything that has magnetic properties can be a magnet

NON-MAGNETIC MATERIALS

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* such as wood, paper and glass, cannot be made into magnets. 
* No magnet content

Poles

Portions of a magnet, usually near its end, where the magnetic force is greatest.

Magnetization

process of making a material temporarily or permanently become magnetic.

Magnetic Field

region of space where a magnet is capable of exerting a force on a magnetic material.

charge

Electric fields surround a _

magnet

magnetic fields surround a _.

positive and negative

Electric fields: start from a … charge and end on a ….charge.

north and south

Outside a magnet, the lines are directed from the --- pole to the ---pole.

south and north

Inside a magnet, they run from the --- pole to -- pole.

FIRST RIGHT HAND RULE

determines the direction of magnetic fields and currents

SECOND RIGHT HAND RULE

use to determine: direction of current; direction of magnetic force ; and direction of magnetic field

Magnetic Field

Produced by a magnet represented by lines.

Tesla

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* Earth’s magnetic field is about 5x10-5 T
* Weber per square meter (Wb/m2) old name for ___.
* Magnitude of magnetic field.

Magnetic Force

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* Attracts and repels when two lines of force are both close together.
* is on a moving charge:
* if an electric charge q moves with a velocity v through a magnetic field B, a ___ is exerted on the charge.

DOPING

Small numbers of dopant atoms can change the ability of a semiconductor to conduct electricity

atoms of various elements are added in small amounts to semiconductors to increase conductivity.

electron affinity

The material with the higher -- will attract more electrons.

MAGNETIC FORCE

SECOND RIGHT HAND RULE

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thumb

Current

SECOND RIGHT HAND RULE

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index finger

MAGNETIC FIELD

SECOND RIGHT HAND RULE

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middle

Parallel Circuit

There are multiple paths for the current to flow through