10.3 Flashlights

# 10.3 Flashlights - Electric Fields Clicker Question If you...

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Electric Fields 11/19/01 Lecture 19 1 Key Concepts: 1. Electric circuits a. Resistance b. Current c. Voltage 2. Power Clicker Question Clicker Question If you remove the 2 batteries from a working flashlight and reinstall them backward so that they make good contact inside, will the flashlight still work? a) Yes b) No Observations About Flashlights • They turn on and off with a switch • More batteries usually means brighter • The orientation of multiple batteries matters • Flashlights dim as batteries age • Sometimes smacking a flashlight brightens it Batteries and Bulbs ac b

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Electric Fields 11/19/01 Lecture 19 2 Electric Circuits + - A complete circuit: a continuous conducting path from one end of the battery to the other end of the battery + - Three Components: 1. Source of electrical energy 2. Load 3. Complete circuit Current… the flow of electric charge + - Current = charge flowing past a specific point in the circuit per unit time. Measured in amperes ampere = coulomb/second I - Voltage is Potential Bulb is Resistance • Battery is like reservoir of elevated water – The higher, the bigger the potential , or voltage • Imagine bulbs as small tubes that let water drain – Resistance is represented by length of tube shorter: less resistance: more current flows longer: more resistance: less current flows Voltage Battery Bulbs in Series Each light bulb presents a “resistance” to the circulating electrical current. Adding more bulbs in series adds to the resistance to the current, so less current flows. Which bulb is brighter? A or B A B + _
Electric Fields 11/19/01 Lecture 19 3 Analogy • There is only one current flowing, and it goes through both bulbs. They will therefore shine with equal brightness. • Imagine exchanging bulbs. Does this change anything? Voltage A B A B + _ Which bulb is brighter? A or B AB + - Resistances/loads in Parallel Currents Merge and Divide at Junctions How much would the current through the battery change if “A” was unscrewed?

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10.3 Flashlights - Electric Fields Clicker Question If you...

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