Science Department - ISP

Chapter 13 - Temperature and Kinetic Theory

Kinetic Theory: Theory explaining the physical properties of objects in terms of the motion of the particles that make up the object.

Temperature: Physical quantity that is proportional to the average kinetic energy of translation of particles in matter. (Macroscopically, it refers to how "hot" or how "cold" an object is.)

Thermometer: Instrument designed to measure temperature. They all depend on some property of matter that changes with temperature.

Coefficient of linear expansion (): Constant of proportionality, characteristic of a given material that measures the change in length per unit length of a solid per degree change in temperature.

Coefficient of volume expansion: Constant of proportionality, characteristic of a given material, that measures the change in volume per unit volume of a solid or liquid per degree change in temperature.

Stress: Distorting force per unit area. (F/A)

Strain: Fractional change in dimensions produced by a stress applied on a body.

Elastic (or Young's) Modulus: Constant of proportionality, characteristic of a material, that gives the ratio of stress to strain in a solid.

State: Physical condition of a system.

Equation of State: Equation relating the pressure, volume and temperature of a substance.

Equilibrium State: When the variables that describe a particular state of a system are the same throughout the system and are not changing in time.

Standard Conditions (STP): Standard temperature and pressure. There values are T = 273 k (0 Celsius) for the temperature, and P= 1.00 atm (1.01E5 Nm-2 ) for the pressure.

Avogadro's Number: Number of molecules in 1 mol of substance. NA = 6.02E23 molecules/mol

Critical Temperature: Temperature at which a gas must be cooled before it can be liquefied by pressure.

Critical Point: Upper limit of the temperature-pressure curve of a substance. It determines the temperature below which a gas will change to liquid if sufficient pressure is applied.

Vapor: Substance below its critical temperature in gaseous state.

Gas: Substance above its critical temperature.

Sublimation: Process whereby at low pressures a solid changes directly into vapor phase without passing through the liquid phase.

Triple Point: The single condition of temperature and pressure at which the solid, liquid, and vapor phases of a substance can coexist in stable equilibrium.

Evaporation: Process by which a liquid changes its phase to become a vapor or gas.

Condensation: The change of phase from a gas or vapor to a liquid.

(Saturated) Vapor Pressure: Pressure of the vapor of a substance when it is saturated. It does not depend on the volume of the container; it increases with temperature. At high temperatures, equilibrium will be reached.

Partial Pressure: The pressure a gas would exert if it alone occupied the whole of its container.

Dalton's Law: The pressure of a mixture of gases is the sum of the partial pressures of its individual constituents. (This is strictly true for ideal gases.)

Relative Humidity: Ratio of the partial pressure to the saturated vapor pressure of water in air at a given temperature, usually expressed as a percent.

Dew Point: Temperature at which the partial pressure of water in air equals the saturated vapor pressure.

Diffusion: Movement of a gas, liquid, or solid within another substance, as a result of the random motion of its particles; one type of particle moves to penetrate into the mass of a second type of particle.

Chapter 14 - Heat

Heat: Energy that is transferred from regions of high temperature to regions of low temperature, or from one body to another because of a difference in temperature.

Thermal Equilibrium: State in which there is no net flow of heat between two bodies; at this point they have the same temperature.

Calorie (cal): Amount of heat necessary to raise the temperature of 1 gram of water by 1 Celsius, from 14.5 Celsius to 15.5 Celsius.

Thermal (Internal) Energy: Sum total of all the potential and kinetic energy associated with the random motions of the particles of a material.

Heat Capacity: Quantity of heat required to raise the temperature of a body by one unit.

Specific Heat: Constant of proportionality that measures the heat capacity of an object.

Calorimetry: Quantitative study of heat exchange.

Calorimeter: Device for measuring thermal energy, that usually consists of nested cups separated by an air space.

Heat of Fusion: Heat required per unit mass to change a substance from solid to liquid at its melting point.

Heat of Vaporization: Heat required per unit mass to change a substance from liquid to vapor at its boiling point .

Latent Heat: Energy transferred when a substance changes its state from solid to liquid, liquid to gas, or solid to gas.

Evaporation: Change of phase from liquid to a gas or vapor.

Conduction: Process of heat transfer through a substance without movement of the substance itself. The rate of transfer depends on the sample length and cross-sectional area, the temperature difference, and the temperature of the material.

Thermal Conductivity: Constant of proportionality, characteristic of a material, that measures the ability of a material to conduct thermal energy. Defined as the energy transfer per unit time per unit cross-sectional area of the conductor, per unit temperature gradient along the conductor.

Thermal Conductor: Substance that has a relatively high thermal conductivity.

Thermal Insulator: Material that does not readily transmit heat; it has a relatively low value for its thermal conductivity.

Convection: Transfer of energy by flow of a liquid or a gas. In natural convection, the fluid flow is caused by temperature differences between one part of the fluid and another. In forced convection, energy is carried away from the source by flow produced by a pump or fan.

Radiation: Heat energy emitted from a body in the form of particles or waves, usually transferred over empty space. It consists essentially of electromagnetic waves.

Chapter 15 - Thermodynamics

Thermodynamics: Study of quantitative relationships between heat and the processes in which energy is transferred as heat, work, or other forms of energy.

System: Any object or set of objects under consideration.

Closed System: Set of one or more objects that may interact with each other, but do not interact with the world outside. This means that there is no net force from the outside, or energy transfer. Because of this, the system's angular momentum, energy, mass, and linear momentum remain constant. A closed system is said to be isolated if no energy in any form passes across its boundaries; otherwise, it is not isolated.

Open System: System that is not isolated from the environment, so mass may enter or leave the system; parts of the system may interact with the environment.

Zeroth Law of Thermodynamics: If two bodies are each in thermal equilibrium with a third body, then they are in thermal equilibrium with each other.

First Law of Thermodynamics: The total energy on a closed system is conserved. For an isolated system, W = Q = 0 and channge in U = 0.

Isothermal Process: Process that takes place at constant temperature.

Adiabatic Process: Process taking place in a system that has perfect thermal insulation, so that heat cannot enter or leave the system and energy can only be transferred by work. Then, Q = 0.

Isobaric Process: Process in which the pressure is kept constant.

Second Law of Thermodynamics (Clausius Statement)

"Heat flows naturally from a hot object to a cold object; heat will not flow spontaneously from a hot object to a cold object."

Heat Engine: Any device that changes thermal energy into mechanical work.

Efficiency: Ratio of the work done by a system or device to the energy input.

Equilibrium: A state of a system in which the properties do not change with time.

Reversible Process: Process in which the pressure, volume, or other properties of a system change, but the system remains in equilibrium throughout the change.

Irreversible Process: Process in which there is not equilibrium as changes take place.

Second Law of Thermodynamics (Kelvin-Plank Statement)

"No device is possible whose sole effect is to transform a given amount of heat completely onto work."

Heat Pump: Device that continually extracts heat from a body and discharges heat at a higher temperature.

Entropy: Measure of disorder in a system; ratio of the heat added to temperature.

Second Law of Thermodynamics (stated in terms of entropy)

"The entropy of an isolated system never decreases; it can only stay the same or increase."

General Statement of the Second Law of Thermodynamics

(1) "The total entropy of any isolated system plus that of its environment increases as a result of any natural process."

(2) "Natural processes tend to move toward a state of greater disorder." (Notice that this statement applies beyond what we consider thermodynamics.)

Chapter 16 - Electrostatics

Electric Charge: Basic property of some elementary particles of matter. It has no operational definition; rather, it is taken as a basic experimental quantity. There are two types of electric charge, conventionally called positive and negative. The charge on a body arises from an excess or deficit of electrons with respect to protons.

Electromagnetic Interaction: Mutual effect between objects (stationary or moving) due to the existence of the electric charge, that falls off with the square of the distance that separate the objects; it is responsible for keeping electrons in orbit and forming bonds between atoms and molecules.

Electricity: Study of the nature and effects of moving or stationary charges.

Charged Body: Object in which an excess or deficiency of electrons exist, so that the body contains a net negative charge or a net positive charge.

* The existence of the electric charge can give rise to forces of two kinds:

(1) Electrostatic or Coulomb Force: Force between stationary charged bodies. These forces are always present between any two objects.

(2) Magnetic Force: Force due to electric charges in motion. These forces arise only when there is relative motion between two electrically charged bodies.

Electric Current: Moving electric charges. Operationally defined as the rate of flow of charge.

Law of Conservation of the Electric Charge

" The algebraic sum of the electric charges in any closed system remains constant. In other words, the net amount of electric charge produced in any process is zero."

Conductor: Material through which electric charges are readily transported. They have "free" electrons that can easily move. Electrons are bound very loosely so they can move about freely through the material.

Insulator: Material through which electric charges are not easily conducted. They have relatively few "free" electrons. Their electrons are very tightly bound to the nuclei.

Semiconductor: Material that has electrical conductivity between that of a good conductor and that of a good insulator. They include silicon, germanium, selenium and carbon and are used in solid-state electronics applications. Usually, they are really poor conductors in pure form, but are made semiconductors by adding certain impurities.

Conduction: Process of electrification by contact. It includes the so-called method of electrification by friction. An electrically charged object is placed in contact with an electrically neutral conductor; some of the excess charges on one object move to the other until balance is reached, so when the objects are separated, they are both equally charged.

Induction: Process of electrification that does not require contact. It requires of three conducting objects, at least one of which is electrically charged. The charged object is brought close to the neutral object without touching it. The electrons in the neutral object move within the object towards to or away from the charged object, depending on the sign of its charge, leaving a net charge of opposite sign at both ends of the neutral object. This is a temporary charge, since no electrons have been added to or taken from the neutral conductor. To make it permanent, a third object must make contact with the originally neutral object to give or take some charges, so when they are separated again all three objects will be charged. The object at the middle will have acquired a net charge opposite to that of the other two.

Electroscope: Simple instrument that consists of a central rod and a flexible leaf of gold or aluminum foil that is free to move. This assembly is insulated from the case.

Coulomb's Law: Law of force between two electrically charged objects, proposed by Charles Augustine Coulomb around 1788. It says that "the force between two charges at rest is directly proportional to the product of the magnitude of the charges and inversely proportional to the square of the distance between them."

Electric Field: Disturbance in the region of space that surrounds an electric charge, due to the presence of the charge at a given point in space. An electric field exists at a point in space if test charge experiences an electric force when placed at the point.

Chapter 17 - Electric Potential and Electric Energy

Electric Potential: Energy required to bring a unit electric charge from infinity to a given point.

Electric Potential Difference: Change in PE per unit charge when an electric charge is moved from one point to another in an electric field.

Equipotential Surface: Surface all points of which are at the same potential. Then, the PD between any two points in such a surface is 0.

Potential: Measure of the electric field at a certain distanced from the source.

Potential Gradient: Change in potential per unit distance.

Absolute Potential: Potential at a point due to the existence of a charge that produces a field at the point.

Electric Dipole: Array made up of two point charges Q, of opposite signs, separated by a distance l.

Capacitor: Combination of two conductors placed near each other, where electric charge can be stored.

Capacitance: Constant of proportionality that measures the ability of a system of conductors and insulators to store electric charge.

Dielectric: Electric insulator, or non-conducting medium.

Chapter 18 - Electric Currents

Electromotive Force (EMF): This term refers to a source of electric energy. This is an unfortunate name, since there is no mechanical force involved here, but is kept foe historical reasons. Sources of emf cannot create energy; they simply transform it from one form into another.

Source of EMF: Device within which non-electric energy can be transformed into electric energy. A source of emf may be thought off as a "charge pump" which converts some no-electric form of energy into electric PE by moving charges against an electric field.

Electrolyte: Liquid conductor that consists of water solutions of acids, bases, or salts. The molecules of the solute are dissociated into charged fragments called ions. When charges flow through an electrolyte, a movement of ions takes place in the liquid.

Cell: Single chemical source of emf. It transforms chemical PE into electric PE.

Battery: Combination of cells.

Circuit: Complete path for electrons to move away from and back to their source. (Another comparable but probably better definition will be given in circuit analysis.)

Electric Current: Moving electric charges. Operationally defined as the rate of flow of charge.

Direct Current: An essentially constant-value current in which the movement of charges is only in one direction.

Resistor: Conductor in which electric energy is dissipated, no matter in which direction the charges flow.

Resistance: Ratio of the potential difference across an electrical element to the current in it. It measures the opposition of the object to the flow of charge through it.

Ohm's Law: "The ratio of the potential difference between any two points in a circuit to the current is constant, and equals to the resistance between the two points."

Fixed Resistor: Electric element with two terminals where other elements may be connected. The PD between its ends is directly proportional to the current through it. Its unit is the ohm.

Resistivity: Proportionality constant that relates the length and cross-sectional area of a given electric conductor to its resistance, at a given temperature.

Alternating Current: Time varying electric current that has one direction during one part of the generating cycle and the opposite direction during the remainder of the cycle.

Chapter 19 - Electric Circuits

Electric Circuit: Conducting loop in which a current can transfer energy from a suitable source to a useful load.

Series Circuit: Electric circuit with components arranged to provide a single conducting path.

Facts about series circuits

1.- The current in all parts of a series circuit has the same magnitude.

2.- The sum of all the separate drops of potential around a series circuit is equal to the applied emf.

3.- The total resistance in a series circuit is equal to the sum of the separate resistances.

Parallel Circuit: Electric circuit in which two or more components are connected across the same two points in the circuit, providing separate paths for the current.

Facts about parallel circuits

1.- The total current in a parallel circuit is equal to the sum of the currents in the separate branches.

2.- The PD across all the branches of a parallel circuit must have the same magnitude.

3.- The reciprocal of the equivalent resistance is the sum of the reciprocals of the separate resistors.

Comparison between series and parallel circuits

Kirchhoff's First Law - Theorem of the Nodes

"The algebraic sum of the currents entering any junction point (node) in a circuit is 0." (Based on the law of conservation of the electric charge.)

Kirchhoff's Second Law - Theorem of the Loops

"The algebraic sum of the changes in potential around any closed path in a circuit is 0." (Based on the law of conservation of energy.)

Recommendations to solve circuits using Kirchhoff's Laws

1.- Assume arbitrary directions for the current through each conductor.

2.- Write KSL for as many loops as possible; make sure that each loop contains al least one new element.

3.- Apply KFL to as many nodes as needed.

4.- Make a system of simultaneous equations to find the unknown currents.

Chapter 20 - Magnetism

Magnetism: The study of the nature and cause of magnetic force fields produced by moving electric charges, and how different substances are affected by them.

Ferromagnetism: The property of a substance by which it is strongly attracted by a magnet. It involves electron spin and the alignment of magnetic moments in domains.

Magnetic Force: Force associated with the motion of electric charges.

Magnetic Field: Disturbance in the region of space surrounding objects in which electric charges are moving. It may be detected because a charge moving in that region of space experiences a force due to its motion. More frequently, it is detected by its effect on a compass needle, which lines up in the direction of the magnetic field.

Curie Temperature: Temperature above which a ferromagnetic substance looses its ferromagnetism.

Solenoid: Tight coil of wire with a diameter that is small compared to its length. When carrying a current, they produce a magnetic field similar to that of a bar magnet.

Hall Effect: Effect that describes the potential difference that develops between the sides of a current carrying conductor when it is placed in a magnetic field. When an electric current is passed through a conductor and a magnetic field is applied at right angles, a PD is produced between two opposite surfaces of the conductor. It is caused by deflection of the moving charge carriers in the magnetic field.

Thermionic Emission: The liberation of electrons from the surface of a heated metal or metal oxide. The energy of the emitted electrons is relatively low, and their rate of emission increases with the temperature of the surface.

Cathode-Ray Tube: Electron tube that converts electrical signals into a pattern on a screen. It forms the basis of the oscilloscope and TV receiver. It consists of an electron gun which produces an electron beam that is focussed onto and moved across a luminescent screen by magnetic and/or electric fields.

Isotopes: Two or more species of the same element differing in their mass number because of differing number of neutrons in their nuclei.

Permeability: Property of a material by which it changes the flux density in a magnetic field from its value in air.

Chapter 21 - Electromagnetic Induction and Faraday's Law

Magnetic Flux: Strength of a magnetic field through an area, based on the idea of the number of lines of force per unit area. It is given by the product of the magnetic induction B and the area.

Induced Current: Electric current in a conductor caused by an emf set up by a changing magnetic field surrounding it.

Electromagnetic Induction: Process by which an emf is set up in a conducting circuit by a magnetic flux linked by the circuit.

Faraday's Law: "An induced emf is produced in any closed circuit if there is a varying magnetic flux. The magnitude of this induced emf is equal to the negative of the time rate of change of magnetic flux through the circuit."

Lenz's Law: "An induced emf is always in such a direction as to oppose the change in magnetic flux that produced it."

Motional Emf: Emf associated with a change in the area of a circuit through which a magnetic flux passes.

Electric Generator: Large machine for converting mechanical energy into electrical energy. It has two sets of coil windings. The relative motion of the two sets of coils induces an electric current.

Dynamo: Small machines for converting mechanical energy into electrical energy. The motion of a coil rotating in a magnetic field induces an alternating current in the windings.

Transformer: Device that changes the effective value of the emf. A typical transformer consists of a primary coil and a secondary coil wound on the same iron core. The ratio of the emf's in the secondary coil to the primary coil is equal to the ratio of the number of turns in the coils.

Mutual Induction: The production of emf in one circuit by changes in the current, and therefore, the magnetic field around, a second nearby circuit.

Self-Induction: The production of an emf in a conductor caused by changes in the current in the conductor itself.