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Electric Current and Ohm’s Law

Electric Current and Ohm’s Law. Section 20.2. What could be wrong?. Continuous flow of electric charge Unit = ampere = amp = A 1 A = 1C/s. Electric Current. Alternating Current Flow of electric charge regularly reverse direction = AC Home, school. Direct Current

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Electric Current and Ohm’s Law

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  1. Electric Current and Ohm’s Law Section 20.2

  2. What could be wrong?

  3. Continuous flow of electric charge Unit = ampere = amp = A 1 A = 1C/s Electric Current

  4. Alternating Current Flow of electric charge regularly reverse direction = AC Home, school Direct Current Flow of electric charge in one direction = DC Battery items Two Types of Current

  5. How does current flow? • Current flow is OPPOSITE of e- flow • Where positive charge would go

  6. Conductor Charge flows easily Metal lattice Copper, Silver Insulator Charge does not flow easily Wood, plastic, rubber, air Conductors and insulators

  7. Resistance • Opposition to the flow of charges in a material • e- move, collide, and lose KE to TE, current decreases

  8. What affects resistance? • Thickness of wire: indirect • The thicker the wire the lower the resistance • Length of wire: direct • The longer the wire the higher the resistance • Temperature of wire: direct • The hotter the wire, the higher the resistance

  9. Zero resistance? • Superconductor = 0 resistance • Material that has 0 resistance when cooled down • Examples: Tin, Aluminum, some alloys

  10. Voltage • In order for charge to flow, the wire must be connected in a complete loop that includes some source of electrical energy

  11. Potential Difference • Charge flows spontaneously from a higher PE to a lower PE • PE depends on position in electric field high PE low PE

  12. Potential Difference • Potential difference is the difference in electrical potential energy between two places in an electric field • Measured in volts • AKA voltage

  13. Voltage Sources • A device is necessary to create the potential difference of charge • Batteries! • Battery—device that converts chemical energy to electrical energy • Voltage of battery = potential difference

  14. Ohm’s Law • Georg Ohm first determined there is a relationship between: • Resistance and voltage and current • Called Ohm’s Law V = I X R

  15. Practice • What is the voltage of a battery if the resistance is 3 ohms and the current is 3 amps? • What is the voltage of a power source if the resistance is 3500 mΩ and the current is 4 A? • What is the current in a wire if the voltage is .5V and the resistance is 2 Ω?

  16. What kind of relationship… • Exists between current and voltage? • Direct proportional • Exists between current and resistance? • Indirect proportional

  17. Reviewing Concepts • List the two types of current • Name two good conductors and two good insulators • What variables affect the resistance of a material? • What causes charge to flow? • What is Ohm’s law?

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