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ELECTRIC CURRENT 2

ELECTRIC CURRENT 2. Ohm’s law shows the relationship between current, potential, and voltage. We need a few more rules to make predictions about current flow through circuits. Rule 1: Conservation of Charge.

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ELECTRIC CURRENT 2

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  1. ELECTRIC CURRENT 2 Ohm’s law shows the relationship between current, potential, and voltage. We need a few more rules to make predictions about current flow through circuits.

  2. Rule 1: Conservation of Charge The number of charges flowing into a point is the same as the number of charges flowing out of a point

  3. 3 amps ? 5 amps

  4. 3 amps 2 amps 5 amps

  5. Rule 2: Conservation of Energy The total drop in potential energy of a circuit is equal to the total voltage of the circuit

  6. SERIES CIRCUITS

  7. The voltage drops across each resistor, but the total voltage drop is still 60 volts.

  8. R1 V1 V2 R2 So, V1 + V2 = 60 volts… And V=IR

  9. R1 V1 V2 R2 So, IR1 + IR2 = IRtotal But the current is the same through R1 and R2.

  10. R1 V1 V2 R2 IRtotal = I (R1 +_R2) or Rtotal = R1 +_R2

  11. Summary: For series circuits the total resistance is equal to the sum of all the resistors in series. Functionally, this is the same as increasing the length of a resistor. As L increases, so does R.

  12. From the Reference Tables

  13. So, back to our problem! R1 V1 V2 2 A R2 R1+ R2 = 30 Ω = total resistance Therefore the total current = V/R =2 amps

  14. V1= 40 volts V2 = 20 volts Remember, IR1 + IR2 = IRtotal So: (2 amps x 20 ohms) = 40 volts and (2 amps x 10 ohms) = 20 volts

  15. PARALLEL CIRCUITS

  16. It R1 R2 I1 I2 The voltage drop across R1 and R2 is the same and It = I1 + I2

  17. It R1 R2 I1 I2

  18. It R1 R2 I1 I2 So:

  19. Summary: For parallel circuits the reciprocal of the total resistance is equal to the sum of the reciprocal of each resistance. Functionally, this is the same as increasing the area of a resistor. As A increases, R decreases.

  20. From the Reference Tables

  21. It R1 R2 I1 I2 Back to our problem

  22. It R1 R2 I1 I2 Notice that the total resistance is less that either one

  23. It R1 R2 I1 I2 We can now calculate the total current…

  24. It= 0.6 amps R1 R2 I1 I2 …and the current through each resistor.

  25. Finally, It= 0.6 amps R1 R2 I2= 0.3 amps I2= 0.3 amps

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