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

• 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

• 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

• 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

• 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

• 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

• 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

• the charge (electron) “pusher.”

• causes current to flow/move.

Volts

Unit for voltage

Alessandro Volta

• Italian physicist

• known especially for the invention of the electrochemical cell, aka the battery in 1800.

CURRENT

• 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

• 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

• opposes the push from the voltage source.

• affects the speed of the current.

Ohms

Unit for Resistance

Georg Ohm

• 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

• 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

• 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

• each + all

• any closed path going through circuit elements.

NODES

• 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

• 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

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

ARTIFICIAL MAGNETS

• can be made using magnetic materials.

• Anything that has magnetic properties can be a magnet

NON-MAGNETIC MATERIALS

• 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

• Earth’s magnetic field is about 5x10-5 T

• Weber per square meter (Wb/m2) old name for ___.

• Magnitude of magnetic field.

Magnetic Force

• 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

thumb

Current

SECOND RIGHT HAND RULE

index finger

MAGNETIC FIELD

SECOND RIGHT HAND RULE

middle

Parallel Circuit

There are multiple paths for the current to flow through