Ch. 20 - Electricity Section 20.1 Electric Charge and Static Electricity p. 600.

Download Ch. 20 - Electricity Section 20.1 Electric Charge and Static Electricity p. 600.

Post on 12-Jan-2016




0 download


  • 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

  • Superconductors

    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



View more >