slogan

slogans


Meeting you was fate, becoming your friend was a choice, but falling in love with you was beyond my control.

I thought that I could love no other
Until, that is, I met your brother.

Love is like fire, whether it will warm your heart or burn your house down, you never know.

To hold your hand feels so sweet, with you I always feel complete.

The spaces between your fingers were created so that another’s could fill them in.

Take my heart and lets never part

Come live in my heart and pay no rent.

It feels like bliss, to get a hug and kiss, from you miss.

My lovely honey Valentine, You make me half insane,
but I still love you very much, my darling little pain.

If I had but one wish to come true, it would be to spend Valentines with you

You are so Fine, Please be Mine, This Valentine.

May love come your way, this Valentine’s day.

Cakes and Candy can’t compare to the sweetness of your love.

Lets dance and Dine, this Valentine

All I really need is love, but a little chocolate now and then doesn't hurt!

When you love someone, all your saved-up wishes start coming out.

I loved you yesterday, I love you still,
I always have, and always WILL.

I see your face when I am dreaming.
That’s why I always wake up screaming.

PHYSICS

Minds on Physics Topics

The Minds On Physics Internet Modules consists of 15 different modules which address the following conceptual ideas. Each module focuses on a topic. That topic is addressed primarily on a conceptual basis. Computational problems are also provided, but typically do not form the central basis of the module. The topics addressed by each module are described below. The objectives are listed elsewhere.

• Kinematic Concepts
  This module has eight sublevels which address such topics as vectors, scalars, distance, displacement, velocity, speed, acceleration, oil drop representations, numerical analysis of data, and average speed and average acceleration calculations.
• Kinematic Graphing
  This module has 11 sublevels which address such topics as the conceptual meaning of slope and area of position-time and velocity-time graphs and the mathematical analysis of such graphs.
• Newton's Laws of Motion
  This module has 12 sublevels which address such topics as mass, inertia, action-reaction forces, equilibrium, balanced vs. unbalanced forces, and the acceleration-net force relationship.
• Vectors and Projectiles
  This module has 10 sublevels which address such topics as vector direction, vector addition, vector resolution, and the horizontal and vertical components of displacement, velocity, acceleration and force for a projectile's motion.
• Forces in 2-Dimensions
  This module has 6 sublevels which address such topics as vector components, equilibrium, the hanging of signs, and inclined planes.
• Momentum and Collisions
  This module has 10 sublevels which address such topics as momentum, impulse, impulse-momentum change theorem, action-reaction forces in a collision, momentum transfer in a collision, and momentum conservation in a collision.
• Work, Energy, and Power
  This module has 10 sublevels which address such topics as work, power, kinetic and potential energy, and the relationship between the mechanical energy of an object and the work done upon or by it.
• Circular and Satellite Motion
  This module has 10 sublevels which address such topics as tangential velocity, centripetal acceleration, centripetal force, inertia, the mathematics of circular motion, satellite motion, universal gravitation, and Kepler's laws of planetary motion.
• Special Relativity
  Not yet available; may be introduced at a future time.
• Electrostatics
  This module has 12 sublevels which address such topics as atomic structure, the nature of charge, insulators, conductors, charging by the methods of friction, induction, and contact, interaction between charged objects, Coulomb's Law, electric fields, and electric field lines.
• Electric Circuits
  This module has 12 sublevels which address such topics as current, voltage, resistance, Ohm's Law, electric power, series and parallel connections, mathematical analysis of circuits, and combination circuits.
• Waves
  This module has 8 sublevels which address such topics as the nature of a wave, properties of a wave and basic wave behaviors such as interference and boundary behavior.
• Sound and Music
  This module has 11 sublevels which address such topics as the nature of a sound wave, properties of a sound wave, intensity level and the deciBel scale, the Doppler effect, resonance, and standing wave patterns for string instruments and open- and closed-end air columns.
• Light and Color
  This module has 9 sublevels which address such topics as the nature of light waves and the electromagnetic spectrum, the phenomenon of polarization, color addition and subtraction, and the use of color filters.
• Reflection and Mirrors
  This module has 11 sublevels which address such topics as the law of reflection, diffuse and regular reflection, image formation, plane mirrors, concave mirrors and convex mirrors.
• Refraction and Lenses
  This module has 11 sublevels which address such topics as refraction, the dependency of the direction of bending upon relative light speed, medium density and index of refraction values, Snell's law, total internal reflection, and converging and diverging lenses.

PHYSICS

electric current

An electric current is a flow of electric charge. In electric circuits this charge is often carried by moving electrons in a wire. It can also be carried by ions in an electrolyte, or by both ions and electrons such as in a plasma.^[1]The SI unit for measuring an electric current is the ampere, which is the flow of electric charge across a surface at the rate of onecoulomb per second. Electric current is measured using a device called an ammeter.^[2]Electric currents can have many effects, notably heating, but they also create magnetic fields, which are used in motors, inductors and generators.

SymbolThe conventional symbol for current is I, which originates from the French phrase intensité de courant, or in English current intensity.^[3][4] This phrase is frequently used when discussing the value of an electric current, but modern practice often shortens this to simply current. The I symbol was used by André-Marie Ampère, after whom the unit of electric current is named, in formulating the eponymous Ampère's force law which he discovered in 1820.^[5] The notation travelled from France to Britain, where it became standard, although at least one journal did not change from using C to I until 1896.

Main article: 

Ohm's law
Ohm's law states that the current through a conductor between two points is directly proportional to the potential difference across the two points. Introducing the constant of proportionality, the resistance,^[7] one arrives at the usual mathematical equation that describes this relationship:^[8]

where I is the current through the conductor in units of amperes, V is the potential difference measured across the conductor in units of volts, and R is the resistance of the conductor in units of ohms. More specifically, Ohm's law states that the R in this relation is constant, independent of the current.^[9]
The abbreviations AC and DC are often used to mean simply alternating and direct, as when they modify current or voltage.^[10][11]

Direct current
Main article: Direct current
Direct current (DC) is the unidirectional flow of electric charge. Direct current is produced by sources such as batteries, thermocouples, solar cells, and commutator-type electric machines of the dynamo type. Direct current may flow in a conductor such as a wire, but can also flow through semiconductors, insulators, or even through a vacuum as in electron or ion beams. The electric charge flows in a constant direction, distinguishing it from alternating current (AC). A term formerly used for direct current was galvanic current.^[12]

Alternating current
Main article: Alternating current
In alternating current (AC, also ac), the movement of electric charge periodically reverses direction. In direct current (DC, also dc), the flow of electric charge is only in one direction.
AC is the form in which electric power is delivered to businesses and residences. The usual waveform of an AC power circuit is a sine wave. In certain applications, different waveforms are used, such as triangular or square waves. Audio and radio signals carried on electrical wires are also examples of alternating current. In these applications, an important goal is often the recovery of information encoded (or modulated) onto the AC signal
Voltage, electrical potential difference, electric tension or electric pressure (denoted ∆V and measured in units of electric potential:volts, or joules per coulomb) is the electric potential difference between two points, or the difference in electric potential energy of a unitcharge transported between two points.^[1] Voltage is equal to the work done per unit charge against a static electric field to move the charge between two points. A voltage may represent either a source of energy (electromotive force), or lost, used, or stored energy (potential drop). A voltmeter can be used to measure the voltage (or potential difference) between two points in a system; often a common reference potential such as the ground of the system is used as one of the points. Voltage can be caused by static electric fields, byelectric current through a magnetic field, by time-varying magnetic fields, or some combination of these three.
An electric current is a flow of electric charge. In electric circuits this charge is often carried by moving electrons in a wire. It can also be carried by ions in an electrolyte, or by both ions and electrons such as in a plasma
 

Ohm's law

AC and DC

Current Electricity - Lesson 3 - Electrical Resistance

Resistance

• Journey of a Typical Electron
• Resistance
• Ohm's Law
• Power Revisited

An electron traveling through the wires and loads of the external circuit encounters resistance. Resistance is the hindrance to the flow of charge. For an electron, the journey from terminal to terminal is not a direct route. Rather, it is a zigzag path that results from countless collisions with fixed atoms within the conducting material. The electrons encounter resistance - a hindrance to their movement. While the electric potential difference established between the two terminals encourages the movement of charge, it is resistance that discourages it. The rate at which charge flows from terminal to terminal is the result of the combined effect of these two quantities.

Variables Affecting Electrical Resistance

The flow of charge through wires is often compared to the flow of water through pipes. The resistance to the flow of charge in an electric circuit is analogous to the frictional effects between water and the pipe surfaces as well as the resistance offered by obstacles that are present in its path. It is this resistance that hinders the water flow and reduces both its flow rate and its drift speed. Like the resistance to water flow, the total amount of resistance to charge flow within a wire of an electric circuit is affected by some clearly identifiable variables.

First, the total length of the wires will affect the amount of resistance. The longer the wire, the more resistance that there will be. There is a direct relationship between the amount of resistance encountered by charge and the length of wire it must traverse. After all, if resistance occurs as the result of collisions between charge carriers and the atoms of the wire, then there is likely to be more collisions in a longer wire. More collisions mean more resistance.

Second, the cross-sectional area of the wires will affect the amount of resistance. Wider wires have a greater cross-sectional area. Water will flow through a wider pipe at a higher rate than it will flow through a narrow pipe. This can be attributed to the lower amount of resistance that is present in the wider pipe. In the same manner, the wider the wire, the less resistance that there will be to the flow of electric charge. When all other variables are the same, charge will flow at higher rates through wider wires with greater cross-sectional areas than through thinner wires.

A third variable that is known to affect the resistance to charge flow is the material that a wire is made of. Not all materials are created equal in terms of their conductive ability. Some materials are better conductors than others and offer less resistance to the flow of charge. Silver is one of the best conductors but is never used in wires of household circuits due to its cost. Copper and aluminum are among the least expensive materials with suitable conducting ability to permit their use in wires of household circuits. The conducting ability of a material is often indicated by its resistivity. The resistivity of a material is dependent upon the material's electronic structure and its temperature. For most (but not all) materials, resistivity increases with increasing temperature. The table below lists resistivity values for various materials at temperatures of 20 degrees Celsius.

Material	Resistivity (ohm•meter)
Silver	1.59 x 10-8
Copper	1.7 x 10-8
Gold	2.4 x 10-8
Aluminum	2.8 x 10-8
Tungsten	5.6 x 10-8
Iron	10 x 10-8
Platinum	11 x 10-8
Lead	22 x 10-8
Nichrome	150 x 10-8
Carbon	3.5 x 10-5
Polystyrene	107 - 1011
Polyethylene	108 - 109
Glass	1010 - 1014
Hard Rubber	1013

As seen in the table, there is a broad range of resistivity values for various materials. Those materials with lower resistivities offer less resistance to the flow of charge; they are better conductors. The materials shown in the last four rows of the above table have such high resistivity that they would not even be considered to be conductors.

Look it Up!

Use the Resistivity of a Material widget to look up the resistivity of a given material. Type the name of the material and click the Submit button to find its resistivity.

	Resistivity of a Material
	What is the resistivity of ? Submit See http://www.physicsclassroom.com/Class/circuits/u9l3b.cfm.

Mathematical Nature of Resistance

Resistance is a numerical quantity that can be measured and expressed mathematically. The standard metric unit for resistance is the ohm, represented by the Greek letter omega - . An electrical device having a resistance of 5 ohms would be represented as R = 5 . The equation representing the dependency of the resistance (R) of a cylindrically shaped conductor (e.g., a wire) upon the variables that affect it is

where L represents the length of the wire (in meters), A represents the cross-sectional area of the wire (in meters2), and  represents the resistivity of the material (in ohm•meter). Consistent with the discussion above, this equation shows that the resistance of a wire is directly proportional to the length of the wire and inversely proportional to the cross-sectional area of the wire. As shown by the equation, knowing the length, cross-sectional area and the material that a wire is made of (and thus, its resistivity) allows one to determine the resistance of the wire.

Investigate!

Resistors are one of the more common components in electrical circuits. Most resistors have stripes or bands of colors painted on them. The colors reveal information about the resistance value. Perhaps you're doing a lab and need to know the resistance of a resistor used in the lab. Use the widget below to determine the resistance value from the colored stripes.

	Resistor Color Code
	1st color 2nd color 3rd color 4th color Submit More info at: http://www.physicsclassroom.com/class/circuits/u9l3b.html