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Homework Help: Amount of charge flowing through a resistor?

  1. Aug 17, 2011 #1
    Amount of charge flowing through a resistor???

    the current through a resistor is 3 mA. What charge will flow through it in 200 seconds?

    if the resistor has a resistance of 2.0 kΩ what will be the power dissipated in it?

    for the first one, i have no idea. i cant seem to find any formula that is relavent to this so im guess the answer is simple but im missing a vital piece of information that would link the dots.

    for the second one i was thinking the power disippated in the resistor would be the same as the resistance, becuase the resistance is stopping anything above 2.0 V to enter the resistor?

    any help is appriated, this is for my exam tomorrow.
     
  2. jcsd
  3. Aug 17, 2011 #2

    Doc Al

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    Staff: Mentor

    Re: Amount of charge flowing through a resistor???

    What's the definition of current?

    No, power is not the same as resistance. But the power dissipated depends on the current and the resistance. (Look it up!)
     
  4. Aug 17, 2011 #3
    Re: Amount of charge flowing through a resistor???

    "Electrical current is a measure of the amount of electrical charge transferred per unit time. It represents the flow of electrons through a conductive material.
    Current is a scalar quantity (though in circuit analysis, the direction of current is relevant). The SI unit of electrical current is the ampere, defined as 1 coulomb/second"

    so its 600 coulombs

    im still confused about power, i've tried looking it up but it doesnt make any sense, is it the same as voltage?

    so V=IxR

    meaning 3 mA x 2 kΩ giving me 6 Volts that are being dissapated in the resistor
     
  5. Aug 17, 2011 #4

    Doc Al

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    Re: Amount of charge flowing through a resistor???

    Current = Charge/Time, thus Charge = Current * Time.

    Redo that calculation.

    No. Read: http://hyperphysics.phy-astr.gsu.edu/hbase/electric/elepow.html#c2"
     
    Last edited by a moderator: Apr 26, 2017
  6. Aug 17, 2011 #5
    Re: Amount of charge flowing through a resistor???

    Ok so, to find the charge in 200 seconds. I multiply 3mA by 200 because charge = current*time

    Giving me 600A ??

    And for the second part I use Power = voltage * current

    So the power dissipated in the resistor = 600 (current) * 2 (resistance) is this wrong ?
     
  7. Aug 17, 2011 #6
    Re: Amount of charge flowing through a resistor???

    Actually for the second part, I'm meant to use power = current squared * resistance. So I'd get 720,000
     
  8. Aug 17, 2011 #7

    Doc Al

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    Re: Amount of charge flowing through a resistor???

    Careful: mA means milli-Amps = 10-3 Amps

    (And the charge would be in Coulombs, not Amps.)

    Same issue with your power calculation.
     
  9. Aug 17, 2011 #8
    Re: Amount of charge flowing through a resistor???

    Ok, cheers mate!
     
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