1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Designing basic circuits to power devices

  1. Mar 22, 2010 #1
    1. The problem statement, all variables and given/known data
    Device requires a terminal voltage of 12 volts and a current of 2 Amps. Design a circuit using as many 3 ohm resistors as needed to properly power this device. The EMF is 24 Volts.

    2. Relevant equations
    Ohm's law: V=IR

    3. The attempt at a solution
    I know how to find equivalent resistance, but I don't know how to dissipate some of the voltage, in this case, get the voltage from 24 down to 12.
  2. jcsd
  3. Mar 23, 2010 #2
    Calculate the resistance of the device from the fact that V=12V and I=2A.
    If the pd across it is to be 12V but the supply is 24V, then you need a circuit in which there is 12V combined across the available 3 ohm resistors and 12V across the device.
    Does that help? Try both a series and parallel circuit to see which will do the job.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook