2 Electric Charge Electrons negatively charged property of matter that creates electric and magnetic forces and interactions.electric charge depends on the imbalance of its protons and electrons.Electrons negatively chargedprotons positively chargedneutrons are neutral (no charge).Like charges repelopposite charges attract.
3 E l e c t r i c c h a r g e L i k e c h a r g e s r e p e l . O p p o s i t e c h a r g e s a t t r a c t .
4 Electric ChargeNegatively charged objects have more electrons than protons.Positively charged objects have fewer electrons than protons.SI unit:coulomb, C.
5 Electric Charge electrical conductor: material in which charges can move freely and that can carry an electric current.electrical insulator:material that does not transfer current easily.Objects can be charged by the transfer of electrons.outermost electrons can be easily transferred from one atom to another.Charging by frictionwhen one material gains electrons and becomes negatively charged, and the other loses electrons and becomes positively charged.
6 INDUCED CHARGES polarization Alignment of charges at surface of an object producing an electric chargePositive & negative charges on opposite sides
7 Charging by Contactcharge a neutral object by touching it with a charged object.The transfer of electrons to the metal doorknob gives the doorknob a net negative charge.When a negative rod touches a neutral doorknob, electrons move from the rod to the doorknob.
8 Static Electricity Static Discharge movement of electrons to relieve a separation in charge
9 Electric Forceforce of attraction or repulsion between objects due to charge.atomic and molecular level is responsible for most of the common forces we can observe.Electric force depends on charge and distance.is proportional to the product of charges on objects.is inversely proportional to square of distance between two objects.
10 Electric Forceregion in space around a charged object that causes a stationary charged object to experience an electric force.
11 ELECTRIC FIELD LINESpoint in direction of electric force on a positive charge.around a positive charge point outward.around a negative charge point inward.Electric field lines never cross one another.show both direction of an electric field and relative strength due to a given charge.More lines are drawn for greater charges to indicate greater force.
15 ELECTRICAL POTENTIAL ENERGY ability to move an electric charge from one point to another.EPE of moving charge decreases because electric field does work on charge.EPE depends on distance between two charged objects for both an attractive and a repulsive electric force.
16 Electrical Potential Energy The electrical potential energy between two negative charges decreases as the distance between them increases.
17 Electrical Potential Energy and Relative Position The electrical potential energy of a charge depends on its position in an electric field.
18 POTENTIAL DIFFERENCEwork that must be done against electric forces to move a unit charge from one point to the other.measured in volts, VVOLTequivalent to one joule per coulomb (1 J/C).aka voltage.
19 Voltage and Current Cell: device that is a source of electric current because of a potential difference (voltage) b/w terminals.Positive & negative.Batteries convert chemical energy into electrical energy.
20 VOLTAGE Measure of energy available to move electrons. Electrical potential difference b/w two points.sets charges in motion.
21 CURRENT rate that electric charges move through a conductor. SI unit: ampere, A.1 amp = 1 C/sbattery is a direct current source b/c charges always move from one terminal to other in same direction.Conventional current= movement of positive charge.direction of current in a wire is opposite direction that electrons move in that wire.
22 Electrical Resistance opposition posed by a material or a device to the flow of current.caused by internal frictionwhich slows the movement of charges through a conducting material.SI unit:ohm, Ω.1 Ω = 1 V/AResistor:special type of conductor used to control current.
23 R V I OHM’S LAW Resistance = voltage/current V: potential difference (V)I: current (A)R: resistanceRVI
24 R V I R = 160 I = V ÷ R V = 120 V I = (120 V) ÷ (160 ) I = ? A light bulb with a resistance of 160 Ω is plugged into a 120 V outlet. What is the current flowing through the bulb?GIVEN:R = 160 V = 120 VI = ?WORK:I = V ÷ RI = (120 V) ÷ (160 )I = 0.75 AIVR
25 Practice with Ohm’s Law VoltsAmps410025151501023094556488
26 Electrical Resistance Conductorshave low resistances.SuperconductorsCertain metals & compounds have zero resistance when their temperature falls below a certain temperature (critical temperature).Semiconductorsintermediate to conductors and insulators.
28 What Are Circuits? Electric circuit: set of electrical components connected so that they provide one or more complete paths for the movement of charges.closed path through which electrons can flowSwitches control the flow of charges in a circuit.
29 SCHEMATIC DIAGRAMSgraphical representation of a circuit that uses lines to represent wires and different symbols to represent components.
30 SCHEMATIC DIAGRAMSA - battery C - light bulbB - switch D - resistor
31 Series Circuits current travels in a single path one break stops the flow of currentcurrent is the same throughout circuitlights are equal brightnesseach device receives a fraction of the total voltageget dimmer as lights are added
33 Parallel Circuits current travels in multiple paths one break doesn’t stop flowcurrent varies in different branchestakes path of least resistance“bigger” light would be dimmereach device receives the total voltageno change when lights are added
35 Household Circuits Combination of parallel circuits too many devices can cause wires to overheatSafety Features:fuseelectrical device that contains a metal strip that melts when current in circuit becomes too great. metal melts, breaking circuitcircuit breakera switch that opens a circuit automatically when the current exceeds a certain value;bimetallic strip bends when hot, breaking circuit
36 Electric Power and Electrical Energy energy that is associated with charged particles because of their positions.SI unit:watt (W).
37 POWER EQUATIONElectrical Powerrate at which electrical energy is converted to another form of energyP: power (W)I: current (A)V: potential difference (V)PVI
38 V P I I = 0.01 A P = I · V V = 9 V P = (0.01 A) (9 V) P = ? P = 0.09 W A calculator has a 0.01-A current flowing through it. It operates with a potential difference of 9 V. How much power does it use?GIVEN:I = 0.01 AV = 9 VP = ?WORK:P = I · VP = (0.01 A) (9 V)P = 0.09 WPIV
39 Electrical Energyenergy use of an appliance depends on power required and time usedE: energy (kWh)P: power (kW)t: time (h)EtP
40 t E P P = 700 W = 0.7 kW E = P · t E = (0.7 kW) (10 h) t = 10 h A refrigerator is a major user of electrical power. If it uses 700 W and runs 10 hours each day, how much energy (in kWh) is used in one day?GIVEN:P = 700 W = 0.7 kWt = 10 hE = ?WORK:E = P · tE = (0.7 kW) (10 h)E = 7 kWhEPt