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Voltage, current and resistance question, can someone please check if this is correct?

  1. Oct 14, 2014 #1
    1. The problem statement, all variables and given/known data

    A 1.5 volt battery is short-circuited by a 2–meter long wire having a resistance of 0.02 ohm per meter. How large is the current flowing through the wire (before the wire or the battery burn out)?

    2. Relevant equations
    Voltage = Ampere x Resistance
    Ampere = Voltage/Resistance

    3. The attempt at a solution

    Ampere = 1.5 V / 0.02 ohm x 2 m (0.04 ohm/m)
    Ampere = 37.5 Amperes
     
  2. jcsd
  3. Oct 14, 2014 #2

    phinds

    User Avatar
    Gold Member
    2016 Award

    "Ampere = 1.5 V / 0.02 ohm x 2 m (0.04 ohm/m)" is not really a good expression but yes, your answer is right and I think you clearly understand what you are doing even if you did not express it well mathematically. Without units, it's just 1.5/.04 = 37.5

    You should express it mathematically in a way that makes the units come out right
     
  4. Oct 14, 2014 #3

    Mark44

    Staff: Mentor

    Your answer is fine, but your work is a little off in the units. In the first line above, you have .02 ohm x 2 m, and get .04 ohm/m. The numbers are right, but the units aren't. They should be .02 ohm/m x 2 m, which results in .04 ohm, not ohm/m.

    Some suggestions:
    Instead of writing this -- 1.5 V / 0.02 ohm x 2 m (0.04 ohm/m) -- as 1.5 V /(0.02 ohm/m x 2m). In other words, use parentheses around the two factors in the denominator. If you write a/bc, most will interpret this as (a/b) times c, rather than a divided by (bc).
     
  5. Oct 14, 2014 #4
    Oh O.k I see...thank you very much, I will adjust my units :)
     
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