Hewitt/Lyons/Suchocki/Yeh, Conceptual Integrated Science

Hewitt/Lyons/Suchocki/Yeh, Conceptual Integrated Science

Conceptual Physical Science 5th Edition Chapter 8: STATIC AND CURRENT ELECTRICITY 2012 Pearson Education, Inc. 2012 Pearson Education, Inc. This lecture will help you understand:

Electric Charge Coulombs Law Electric Field Electric Potential Voltage Sources

Electric Current Electrical Resistance Ohms Law Electric Circuits Electric Power 2012 Pearson Education, Inc. Electric Force and Charge Electric force: a fundamental force of nature can attract some objects and repel others Electric charge: fundamental quantity underlying electric force and all

electric phenomena comes in two kinds: positive such as protons negative such as electrons 2012 Pearson Education, Inc. Electric Force and Charge Fundamental rule for electricity: Like charges repel; unlike charges attract. 2012 Pearson Education, Inc. Electric Force and Charge

Protons positive electric charges repel positives, but attract negatives Electrons negative electric charges repel negatives, but attract positives Neutrons neutral electric charge 2012 Pearson Education, Inc. Electric Force and Charge atom is normally electrically neutral

same number of electrons outside nucleus as protons in the nucleus outer electrons in metals - loosely bound - can move freely - can flow - can join with other atoms. 2012 Pearson Education, Inc. Electric Force and Charge Atom losing 1 or more electrons positive ion Atom gaining 1 or more electrons negative ion Amount of work varies in pulling electrons from atoms of different substances - very little for metals and other good

conductors - more work for rubber and other good insulators 2012 Pearson Education, Inc. Conductors and Insulators Electric Conductors Materials that allow easy flow of charged particles. outermost electrons of atoms attracted loosely and are easily dislodged as in metals. innermost electrons strongly attracted to nucleus Electric Insulators

Materials having tightly bound electrons. 2012 Pearson Education, Inc. Electric Charge CHECK YOUR NEIGHBOR When you brush Fidos fur and scrape electrons from it, the charge of Fidos fur is A. B. C. D. positive. negative.

both A and B. neither A nor B. 2012 Pearson Education, Inc. Electric Charge CHECK YOUR ANSWER When you brush Fidos fur and scrape electrons from it, the charge of Fidos fur is A. B. C. D.

positive. negative. both A and B. neither A nor B. Explanation: And if electrons were scraped off the brush onto Fidos fur, the fur would have a negative charge. 2012 Pearson Education, Inc. Electric Charge Conservation of Charge In any charging process, no electrons are created or destroyed.

Electrons are simply transferred from one material to another. 2012 Pearson Education, Inc. Coulombs Law Coulombs Law For a pair of charged objects much smaller than the distance between them, force between them varies directly as the product of their charges and inversely as the square of the separation distance F k

2012 Pearson Education, Inc. qq 1 2 2 d Coulombs Law Unit of charge is measured in coulombs, C. The charge of an electron is the fundamental charge = 1.6 10-19 C. k is Coulombs proportionality constant 9.0 109 N

m2/C2 that converts units to force in Coulombs law like signs of charge force is repulsion unlike signs of charge force is attraction 2012 Pearson Education, Inc. Coulombs Law Differences and similarities between gravitational and electrical forces: Gravity only attracts. Electricity can both attract and repel. Both forces can act between things that are not in contact with each other. Both forces act in a straight-line direction

between masses or charges. A force field surrounds both: Gravitational field for mass and electric field for charge. 2012 Pearson Education, Inc. Coulombs Law CHECK YOUR NEIGHBOR According to Coulombs law, a pair of particles that are placed twice as far apart will experience forces that are A. B. C. D.

half as strong. one quarter as strong. twice as strong. four times as strong. 2012 Pearson Education, Inc. Coulombs Law CHECK YOUR ANSWER According to Coulombs law, a pair of particles that are placed twice as far apart will experience forces that are A. B. C.

D. half as strong. one quarter as strong. twice as strong. four times as strong. Explanation: Note the similarity to questions about gravity. 2012 Pearson Education, Inc. Coulombs Law Charge Polarization Molecules in solids cant move from their relatively

stationary positions, but their centers of charge can move. This distortion of charge in the atom or molecule is electric polarization. 2012 Pearson Education, Inc. Polarization Charge polarization Why a charged rubber balloon sticks to a wall. The charged balloon induces polarization of molecules or atoms in the wall. Negative charges on balloon

pull positive sides of molecules near it. Hence a slightly positive induced surface charge on the wall. The balloon sticks. 2012 Pearson Education, Inc. Electric Field (E) Electric field: occupies the space that surrounds any charged object

is a vector quantity (having magnitude and direction) magnitude of field at any point is force per unit charge obeys the inverse-square law for a point source E k q2 d E E F Eq 1 + 2012 Pearson Education, Inc.

q 1 Electric Field Field lines: used to visualize electric field show direction of electric fieldaway from positive and toward negative show intensity of electric field: bunched together field is strongest lines farther apart field is weaker 2012 Pearson Education, Inc.

Electric Field Both Lori and the spherical dome of the Van de Graaff generator are electrically charged. 2012 Pearson Education, Inc. Electric Potential Energy (U) Electric potential energy Energy possessed by a charged particle due to its location in an electric field. 2012 Pearson Education, Inc.

Electric Potential Energy Work is required to push a charged particle against the electric field of a charged body. (a) The spring has more elastic PE when compressed. (b) The small charge similarly has more PE when pushed closer to the charged sphere. In both cases, the increased PE is the result of work input. 2012 Pearson Education, Inc.

Electric Potential Energy (U) Electric Potential Energy Released particle accelerates away from the sphere electric PE changes to KE Q Qq U k d 2012 Pearson Education, Inc. q

Electric Potential Energy Electric Potential Energy Batteries and generators pull negative charges away from positive ones, doing work to overcome electrical attraction The amount of work depends on number of charges and separation distance Work done by a battery or generator is then available to a circuit as electrical PE 2012 Pearson Education, Inc. Electric Potential (V) Electric potential: electric potential energy per charge

energy that a source provides to each unit of charge Electric potential = electric potential energy charge V U q V k Q d V Ed 2012 Pearson Education, Inc. E

d Electric Potential Electric potential and voltage are one and the same. Unit of measurement is the volt. 1 joule 1 volt coulomb 2012 Pearson Education, Inc. Electric Potential

CHECK YOUR NEIGHBOR Electric potential energy is measured in joules. Electric potential, on the other hand (electric potential energy per charge), is measured A. B. C. D. in volts. in watts. in amperes. also in joules.

2012 Pearson Education, Inc. Electric Potential CHECK YOUR ANSWER Electric potential energy is measured in joules. Electric potential, on the other hand (electric potential energy per charge), is measured A. B. C. D. in volts. in watts.

in amperes. also in joules. 2012 Pearson Education, Inc. Conductors and Insulators CHECK YOUR NEIGHBOR When you buy a water pipe in a hardware store, the water isnt included. When you buy copper wire, electrons A. B. C. D.

must be supplied by you, just as water must be supplied for a water pipe. are already in the wire. may fall out, which is why wires are insulated. None of the above. 2012 Pearson Education, Inc. Conductors and Insulators CHECK YOUR ANSWER When you buy a water pipe in a hardware store, the water isnt included. When you buy copper wire, electrons A. B.

C. D. must be supplied by you, just as water must be supplied for a water pipe. are already in the wire. may fall out, which is why wires are insulated. None of the above. Explanation: Even when you get an electric shock, the source of electrons is your own body. The shock occurs when the random motion of electrons becomes an energetic motion in one direction. Ouch! 2012 Pearson Education, Inc.

Voltage Sources Voltage Sources Potential difference exists when ends of electrical conductor are at different electric potentials. Batteries and generators are common voltage sources. Charges in a conductor tend to flow from higher potential to lower potential. The flow of charges persists until both ends reach the same potential. Without potential difference, no flow of charge. 2012 Pearson Education, Inc. Battery Animation

https://www.youtube.com/watch? Voltage Sources Electric potential difference (continued) Example: water from a higher reservoir to a lower oneflow continues until no difference no flow of charge occurs when potential difference is zero 2012 Pearson Education, Inc. Voltage Sources Electric potential difference (continued) Water and electric circuits compared

2012 Pearson Education, Inc. Voltage Sources Electric potential difference in chemical batteries work by chemical disintegration of zinc or lead in acid energy stored in chemical bonds is converted to electric PE Battery Animation https://www.youtube.com/watch?v=HhxtfULIO7 2012 Pearson Education, Inc.

Electric Current Sustained electric current requires suitable voltage source works by pulling negative charges apart from positive ones (available at the terminals of a battery or generator) energy per charge at terminals provides the difference in potential (voltage) to provide electrical pressure to move electrons through a circuit 2012 Pearson Education, Inc. Electric Current Electric current: is the flow of electric charge

in metal conduction electrons in fluids positive and negative ions measured in amperes One ampere is the rate of flow of 1 coulomb of charge per second or 6.25 billion billion electrons per second. Actual speed of electrons is slow through a wire, but electric signal travels near the speed of light. 2012 Pearson Education, Inc. Electric Current CHECK YOUR NEIGHBOR Which of these statements is true? A. B.

C. D. Electric current is a flow of electric charge. Electric current is stored in batteries. Both are true. Neither are true. 2012 Pearson Education, Inc. Electric Current CHECK YOUR ANSWER Which of these statements is true? A.

B. C. D. Electric current is a flow of electric charge. Electric current is stored in batteries. Both are true. Neither are true. Explanation: Voltage, not current, is stored in batteries. The voltage will produce a current in a connecting circuit. The battery moves electrons already in the wire, not necessarily those in the battery. 2012 Pearson Education, Inc.

Electric Current Electric current may be DCdirect current charges flow in one direction ACalternating current charges alternate in direction Accomplished in a generator or alternator by periodically switching the sign at the terminals 2012 Pearson Education, Inc. Electrical Resistance Electrical resistance:

describes how well a circuit component resists the passage of electric current defined as the ratio of energy-source voltage to the current moving through the energy receiver measured in ohms after 19th century German physicist Georg Simon Ohm 2012 Pearson Education, Inc. Electrical Resistance Factors affecting electrical resistance: thin wires resist electrical current more than thicker wires long wires offer more electrical resistance materials of wire:

copper has a low electrical resistance, so it is used to make connecting wires rubber has an enormous resistance, so it is used in electrical insulators temperature: higher temperature (greater jostling of atoms), greater resistance 2012 Pearson Education, Inc. Electrical Conductors Semiconductors materials that are neither good conductors nor good insulators, whose resistance can be varied Superconductors certain metals that acquire infinite conductivity

(zero resistance) at temperatures near absolute zero 2012 Pearson Education, Inc. Ohms Law Ohms Law relationship between current, voltage, and resistance Current in a circuit varies in direct proportion to the potential difference (voltage) and inversely with the resistance: voltage V current

or I resistance R 2012 Pearson Education, Inc. Ohms Law CHECK YOUR NEIGHBOR When you double the voltage in a simple electric circuit, you double the A. B. C. D.

current. resistance. Both of the above. Neither of the above. 2012 Pearson Education, Inc. Ohms Law CHECK YOUR ANSWER When you double the voltage in a simple electric circuit, you double the A. B. C.

D. current. resistance. both of the above. neither of the above. Explanation: This is a straightforward application of Ohms Law. Current 2012 Pearson Education, Inc. voltage . resistance

Ohms Law Electric shock damaging effects of shock result from current passing through the body electric potential difference between one part of your body and another part depends on body condition and resistance, which can range from 100 ohms to 500,000 ohms 2012 Pearson Education, Inc. Ohms Law Prongs on electric plugs and sockets: two flat prongs for the current-carrying double wire,

one part live and the other neutral third prong is longer and the first to be plugged into socket; path to ground prevents harm to user if there is an electrical defect in the appliance 2012 Pearson Education, Inc. Electric Circuits Electric circuits: any closed path along which electrons can flow for continuous flow no gaps (such as an open electric switch) 2012 Pearson Education, Inc.

Electric Circuits Devices connect to a circuit in one of two ways: Series Parallel 2012 Pearson Education, Inc. Electric Circuits Series: A single-pathway circuit for electron flow A break anywhere in the path results in an open circuit; electron flow ceases Total resistance adds, more devices, less

current 2012 Pearson Education, Inc. Electric Circuits Parallel: A branched pathway is formed for the flow of electrons A break in any path doesnt interrupt flow in other paths A device in each branch operates independently of the others Total current in the branches add 2012 Pearson Education, Inc. Electric Circuits

Parallel circuits and overloading Homes are wired in parallel. As more and more devices are connected, more current moves through the wires. Each device can carry a certain amount of current before overheating. Excessive current can result in a fire. 2012 Pearson Education, Inc. Electric Circuits Safety fuses wires melt when current is excessive connected in series along supply line to prevent overloading

commonly replaced by circuit breakers Circuit breaker automatic switch that turns off when the current is excessive 2012 Pearson Education, Inc. Electric Circuits CHECK YOUR NEIGHBOR When two identical lamps in a circuit are connected in parallel, the total resistance is A. B.

C. D. less than the resistance of either lamp. the same as the resistance of each lamp. less than the resistance of each lamp. none of the above. 2012 Pearson Education, Inc. Electric Circuits CHECK YOUR ANSWER When two identical lamps in a circuit are connected in parallel, the total resistance is

A. B. C. D. less than the resistance of either lamp. the same as the resistance of each lamp. less than the resistance of each lamp. none of the above. Explanation: Resistors in parallel are like extra lines at a checkout counter. More lines means less resistance, allowing for more flow. 2012 Pearson Education, Inc.

Electric Circuits CHECK YOUR NEIGHBOR Consider a lamp powered by a battery. Charge flows A. B. C. D. out of the battery and into the lamp. from the negative terminal to the positive terminal. with a slight time delay after closing the switch. through both the battery and the lamp. 2012 Pearson Education, Inc.

Electric Circuits CHECK YOUR ANSWER Consider a lamp powered by a battery. Charge flows A. B. C. D. out of the battery and into the lamp. from the negative terminal to the positive terminal. with a slight time delay after closing the switch. through both the battery and the lamp. Explanation:

Remember, charge is already in all parts of the conducting circuit. The battery simply gets the charges moving. As much charge flows in the battery as outside. So charge flows through the entire circuit. 2012 Pearson Education, Inc. Electric Power Electric power rate at which electric energy is converted into another form in equation form: power = current voltage in units: watts Example: 100-watt lamp draws

0.8 ampere 2012 Pearson Education, Inc.

Recently Viewed Presentations

  • Soc3306a - University of Western Ontario

    Soc3306a - University of Western Ontario

    Soc3306a Individual Assignment 6
  • Additional Concepts In this module additional concepts that

    Additional Concepts In this module additional concepts that

    מַבְזְקִים mavzeQIM shakers, castors פִּלְפֵּל PILpel pepper (vegetable & spice) סֻכָּר suKAR sugar תֵּה\טֵה TEH tea קַנְקַנִּים קַנְקַן עֲמֻקּוֹת עֲמֻקָּה עֲמֻקִּים עָמֹק\עָמוֹק עִבְרִית qanqaNIM qanQAN amuQOT amuQAH amuQIM aMOQ תַּעְתִּיק ...
  • Presentación de PowerPoint - Sanitation and Water for All

    Presentación de PowerPoint - Sanitation and Water for All

    In Costa Rica we have an Annual Report on the State of the Nation, made by the Universities Council and with the participation and validation of the different stakeholders, which include: Trends on water supply and sanitation and definition of...
  • 3856535 - Amazon S3

    3856535 - Amazon S3

    Microencapsulation is a process by which very tiny droplets or particles of liquid or solid material are surrounded or coated withacontinuous film of . polymeric material. The product obtained by this process is called as micro particles, microcapsules. Particles having...
  • Dendroclimatology in Putnam County - DePauw University

    Dendroclimatology in Putnam County - DePauw University

    Dr. Vanessa Fox as a resource. Insert core in tree and rotate clockwise til you hit the center. Pull core out by rotating core in the opposite direction. Put the core into two joined straws. Seal and write location of...
  • Geometry - Mrs Sloman's classes 2014

    Geometry - Mrs Sloman's classes 2014

    Adjacent angles. Adjacent angles are next to each other. They share a vertex (point) and line. Complementary and supplementary angles. Complementary angles add to 90 degrees, and therefore occur within a right angle. ... Geometry Last modified by:
  • Chapter Seven: Abbasid Decline and the Spread of Islamic ...

    Chapter Seven: Abbasid Decline and the Spread of Islamic ...

    Indian achievements were passed to Arabs Colonies of Arabs settled along India's coasts, adopted local customs Provided staging points for Islamic expansion The Coming of Islam to South Asia 10th Century- a Turkish dynasty gained power in Afghanistan 12th Century-...
  • Treatment of Depression in Children & Adolescents Saundra

    Treatment of Depression in Children & Adolescents Saundra

    Inhibit conversion of Tylenol 3 to morphine (P450 2D6) Suicidal thoughts - 4% of pts SSRIs - predicting remission 50-60% of patients get response with 1st SSRI 30% of patients get into remission with 1st medication trial Predictors of remission...