Ch. 20 - Electricity Section 20.1 Electric Charge and Static Electricity p. 600.
Post on 12-Jan-2016
Ch. 20 - ElectricitySection 20.1Electric Charge and Static Electricityp. 600
Electric ChargeCauses subatomic particles to attract/repel2 types+ and Everything affected by charge
Neutral atom = protons & e-sGain e-s = - ion Lose e-s = + ionExcess/shortage of e-s produce net chargeCoulomb (C) - SI unit of electric charge 6.24 x 1018 e-s = 1 C
Electric ForcesOpposite charges attractElectric force depends on charge & distance2x distance = electric forceStronger than gravityHold atoms together
Electric FieldsThe effect electric charge has on other chargesStrength depends on amt of charge producing field & distance from chargeExerts forces on charged object placed in field.More net charge object has, greater force on it
Static Electricity and ChargingStatic Electricitynet accumulation of electric charges on an objectCharge can be transferred byFrictionContactInduction
Static Electricity and ChargingDuring charge transfer, total charge same before & after transferLaw of conservation of charge
Charging by frictione-s move from hair to balloonAtoms in rubber >attraction for e-sBalloon net chargeHair net + charge - -+ + +
Charging by contactTouch electrically charged object you become chargedSphere still has net charge, but reducedVan de Graaff generator
Charging by InductionTransfer of charge w/o contact btwn materialsWalk across carpetPick up extra e-s; net chargeRepels e-s in doorknobLeaves net + charge on doorknob closest to handDoorknob overall charge neutral, but charges moved within it
Static DischargeOccurs when pathway forms for charges to moveAir becomes charged when hand near doorknobAir provides path for e-s
Static Discharge lightningCharge built up from friction btwn moving air masses in clouds- charge in bottom of cloud induces + charge in groundCharge in cloud increasesAttraction increasesAir charged pathway for e-s Lightning 5:06
Chapter 20.2Electric Current and Ohms Lawp. 604
Electric CurrentContinuous flow of electric chargeSI unit is ampere, or amp (A)2 types:Direct current (DC)Alternating current (AC)
Direct CurrentCharge flows in 1 directionMost battery opperated devicesFlashlightsRemotes
Alternating CurrentCurrent that regularly reverses its directionElectric current in homes, businesses, & schools often use AC
Electric current in a flashlighte-s flow from - to + terminalCurrent in opposite direction!Scientists define current as direction + charges flow
Conductorsmaterial that allows e-s to flow easilyMetals like copper and silverMade of ions in a latticeions - atoms that gained or lost e-sIons not free to moveEach ion has e-s loosely held Free e-s conduct charge
Insulatorsmaterial that doesnt allow e-s to move through it easilye- are tightly heldex: plastic, wood, rubber, glass
Resistancee-s in electric curent collideopposes flow of e-selectrical energy converted to thermal energy & lightmeasured in ohms ()Thickness, length, temp affect resistance
Resistance depends on..wire thicknessmore resistance in thinner wiresmilkshake in thin v.s. thick strawwire length more resistance in longer wiresTemphigh resistance at high tempse-s collide more often
Can resistance ever be 0?Superconductors produce near zero resistance when cooled to low temps.
VoltagePotential Difference (voltage)diff in electrical potential btwn 2 places in electric fieldSimilar to PE diff of water at top and bottom of fountainlarge separation of charge creates high voltageLarge fountain high PEpush causing e- to move from - to +measured volts (V)
Voltage sourcesFountains pump water to top, voltage source increases PE of electric chargesbatteriessolar cellsgenerators
Ohms Lawincreasing voltage increases currentIncreasing resistance decreases current
A lightbulb with a resistance of 160 is plugged into a 120-V outlet. What is the current flowing through the bulb?
GIVEN:R = 160 V = 120 VI = ?
ElectroscopeElectroscopeinstrument that detects presence of electrical chargesleaves separate when they gain + or - charge