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Electric Hazards

Electric Hazards. Lethal current - 100 mA causes ventricular fibrillation Larger current - 1 A does not stop heart causes burns Resistance of human body 10 4 - 10 6  when dry 10 3  when wet. The Electric Battery. Source of voltage or potential difference can make charges move!.

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Electric Hazards

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  1. Electric Hazards • Lethal current - 100 mA • causes ventricular fibrillation • Larger current - 1 A • does not stop heart • causes burns • Resistance of human body • 104 - 106 when dry • 103 when wet Circuits

  2. The Electric Battery • Source of voltage or potential difference • can make charges move! Current & Resistance

  3. Battery Model • Energy per unit charge delivered by a battery to the charge carriers it transports against the field • ξ is the battery’s characteristic emf • ξth is the energy per unit charge lost to thermal energy Current & Resistance

  4. Battery Model – con’t A chemical battery a chemical reaction to transport charge carriers to the positive electrode Current & Resistance

  5. Batteries in Series • The emf, ξ, of batteries connected in series, adds Current & Resistance

  6. Electrostatic Potential and the Roller Coaster Analogy • The potential is decreasing as it gets closer to the negative plate. Current & Resistance

  7. Loop Rule Circuits

  8. DC Circuits – Circuit Symbols BatteryCapacitorResistor Wire Switch Ground Circuits

  9. Symbol for battery resistor battery Current & Resistance

  10. Resistors circuit symbol what is the resistance of this resistor? Try some others. Current & Resistance

  11. Adding Resistors • In series: • In parallel: Circuits

  12. Resistance • Rank the configurations in order of increasing resistance. Series Parallel Circuits

  13. Circuit Elements in Series Circuits

  14. Calculate Resistance, Current • A 12-V battery causes a current of 0.60 A through a resistor. (a) What is its resistance? (b) How many joules of energy does the battery lose in a minute? Current & Resistance

  15. Loop Rule Circuits

  16. Resistance, Current, Voltage • Determine (a) the equivalent resistance of the circuit, (b) the current through each resistor, and (c) the voltage across each resistor. Circuits

  17. Circuit Elements in Parallel Circuits

  18. Consider these two circuits... Series How does Req compare between two circuits? Parallel Circuits

  19. Junction Rule Circuits

  20. Resistance, Voltage • Determine (a) the equivalent resistance of the circuit and (b) the voltage across each resistor. Circuits

  21. Rank in order of brightness • Rank bulbs 1 through 6 in order of descending brightness. • Brightness is proportional to power • Now assume the filament in B6 breaks. Again rank the bulbs in order of descending brightness. Circuits

  22. Practice Problems • Determine the equivalent resistance and the current through R1 for the circuits shown. Assume R1 = 10, R2 = 20 , and R1 = 30 , and the battery is 12 V. Circuits

  23. E6 - Activity • Exploration of Physics • E&M • Resistive circuits • Do each of the 5 circuits – set all to 50 ohms • Calculate I, V, and P for each resistor and then check answers in the program • Group Problems • E6B.3, E6B.4, E6S.3, E6S.6 Current & Resistance

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