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Relationship between voltage, power and current

  1. Jan 23, 2017 #1
    • Misplaced homework thread moved here by moderator, hence no template.
    Hy,
    If we double the voltage than what will be double
    A. power
    B. Current
    C. Resistance
    D. Both a & b
     
  2. jcsd
  3. Jan 23, 2017 #2

    Svein

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    As usual: It depends. You have not specified the context. A drawing would help.
     
  4. Jan 23, 2017 #3
    When we double the voltage in a simple electric circuit, we double the
    A. Current
    B. Power
    C. Resistance
    D. Both current and power
     
  5. Jan 23, 2017 #4

    davenn

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    you still haven't specified the circuit setup
    until you fix (state) a couple of the variables, your Q cannot be answered

    Dave
     
  6. Jan 23, 2017 #5
    Actually problem is that
    This question is on the text book which is recommended by government.
     
  7. Jan 23, 2017 #6
    So there is not show any circuit
     
  8. Jan 23, 2017 #7

    davenn

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    so, so let me provide you with a circuit ......

    upload_2017-1-23_18-22-49.png

    a nice simple one, a battery and a resistor

    do you know Ohm's Law ? ....
     
  9. Jan 23, 2017 #8
    Yes I know
     
  10. Jan 23, 2017 #9

    davenn

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    OK, good

    so you have 10V across a 10 Ohm resistor ...
    what is the current flowing in that circuit ?

    show me your working :smile:
     
  11. Jan 23, 2017 #10
    1 A
     
  12. Jan 23, 2017 #11

    davenn

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    correct

    so if you now increase the voltage to 20 V, what is the current in the circuit ?
     
  13. Jan 23, 2017 #12
    2 A
     
  14. Jan 23, 2017 #13

    davenn

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    correct :smile:

    so next, what is the formula for finding power ?
     
  15. Jan 23, 2017 #14
    P = I V
    P= I (2) R
    P = V (2) / R
     
  16. Jan 23, 2017 #15

    davenn

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    Yup
    for ease we can use your first choice P = I x V

    work out the two power levels for the examples we have just done

    then answer your original Q .....




    Dave
     
  17. Jan 23, 2017 #16
    Mean D option is correct
     
  18. Jan 23, 2017 #17

    davenn

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    yes, well done :smile:

    wasn't too difficult to work out, huh :wink:
    .

    Dave
     
  19. Jan 23, 2017 #18
    Thanks
    But
    Is this answer corrected. If current is double
    P = 2 I * 2 V
     
  20. Jan 23, 2017 #19

    davenn

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    unlike voltage or resistance, current cannot just change
    current is a RESULT of a given voltage across a given resistance
    That is, current can ONLY change IF the voltage OR the resistance changes

    And the power, in Watts, dissipated in a circuit, in our circuits above ( in the resistor)
    is always related to the voltage across the resistance divided by the resistance

    so for a fixed resistance, if the voltage is doubled, then the current is doubled and therefore so is the power dissipated


    Dave
     
  21. Jan 23, 2017 #20
    Power dissipated mean?
     
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