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Homework Help: Internal resistance and electromotive force problem

  1. Aug 10, 2005 #1
    help me with this please... i just couldn't get it.

    1) a complete circuit consists of a 12.0 V battery with a 4.50 ohm resistor and switch. the internal resistance of the battery is 0.30 ohms when switch is open. what does the voltmeter read when placed:

    a. across the terminal of the battery when the switch is open
    b. across the resistor when the switch is open
    c. across the terminal of the battery when the switch is closed
    d. across the resistor when the switch is closed

    2) when the switch S is open, the voltmeter V reads 2.0 V. when the switch is closed, the voltmeter reading drops to 1.50 V and the ammeter reads 1.20 A. find the emf (electromotive force) and the internal resistance of the battery. assume that the two meters are ideal so they don't affect the circuit.
     
  2. jcsd
  3. Aug 10, 2005 #2

    Andrew Mason

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    Science Advisor
    Homework Helper

    V=IR. Ohm's law.

    AM
     
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