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22-1 Current & Circuits

22-1 Current & Circuits. Potential Difference. Charges can “lose” potential energy by moving from a location at high potential (voltage) to a location at low potential . Charges will continue to move as long as the potential difference (voltage) is maintained. Producing Electric Currents.

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22-1 Current & Circuits

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  1. 22-1 Current & Circuits

  2. Potential Difference Charges can “lose” potential energy by moving from a location at high potential (voltage) to a location at low potential. Charges will continue to move as long as the potential difference (voltage) is maintained.

  3. Producing Electric Currents • When 2 conducting spheres touch, charges flow from the sphere with higher potential difference to the one at a lower difference • Flow of charged particles is called electriccurrent • Flow of positive charges is called conventional current • Flow stops when this potential difference is equal • How could you keep the flow going?

  4. Electric Current • Keeping the Potential difference changing requires a pump that is powered by an external force • Galvanic cell  Chemical energy to electricity • Photovoltaic cell  Solar to electrical • Generators  Mechanical to electrical

  5. Electric Circuits • Closed loop where charges can flow • Includes a charge pump  increases PE from A-B • Device that reduces the PE from B back to A • Converts to some other form of energy • Motor converts electric energy to  • Lamp converts electric energy to 

  6. Generators Device that converts mechanical energy to electrical energy. Turn a loop of wire between magnets. Energy lost due to thermal energy ***Friction Generator

  7. Rates of Charge Flow • Power is the rate at which work is done • If a generator transfers 1 J of KE to electric energy per 1 sec • 1 J / sec = 1 Watt • The energy carried by an electric current depends on the charge transferred and the potential difference which it crosses

  8. Electric Current • A sustained flow of electric charge past a point is called an electric current. • Specifically, electric current is the rate that electric charge passes a point, soCurrent = Charge or I = q/t Time = 1 Ampere

  9. Energy Transfer • Finding power • Power is the amount of energy delivered to the motor per second • P = IV • If the current through a motor is 3.0 A, and the potential difference is 120 J of energy, what is the power of the motor • I = 3.0 A V = 120 J/C • (3.0 A)(120 J/C) = 360 J/s = 360 Watts (W)

  10. Problem • A 6.0 V battery delivers a 0.50 A current to an electric motor that is connected across it terminals. • A) What is the power run by he motor? • B) If the motor runs for 5.0 minutes, how much energy is delivered? • A) I = 0.50 A V = 6.0 V • = (0.50 A)(6.0 V) = 3.0 W • B) Power = Energy / Time = P = E/t • E = Pt • (3.0 W)(5.0 min x 60s/1 min) = 9.0 x 102 J

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