DC Circuits

EXAMPLE PROBLEM ON OHM'S LAW: The Basic Circuit

Question
An emf source of 6.0V is connected to a purely resistive lamp and a current of 2.0 amperes flows. All the wires are resistance-free. What is the resistance of the lamp?

Hints

  1. Where in the circuit does the gain in potential energy occur?
  2. Where in the circuit does the loss of potential energy occur?
  3. What is Ohm's Law?
Solution
The gain of potential energy occurs as a charge passes through the battery, that is, it gains a potential of =6.0V. No energy is lost to the wires, since they are assumed to be resistance-free. By conservation of energy, the potential that was gained (i.e. =V=6.0V) must be lost in the resistor. So, by Ohm's Law:
    V = I R

    R=V/I

    R = 3.0 


Figure 1 Diagram of the circuit in this problem.


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