Solving a Circuit: What Will the Voltmeter Show?

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SUMMARY

The discussion centers on a circuit analysis problem involving an electromotive force (emf) source and a bulb with equal resistance. The voltmeter, which has a high resistance, indicates a voltage of 6 volts when the bulb is operational. When the bulb burns out, the emf can be calculated using the equation EMF = 2IR, resulting in an emf of 12 volts. This conclusion is derived from the relationship between current, resistance, and voltage in the circuit.

PREREQUISITES
  • Understanding of basic circuit theory
  • Familiarity with Ohm's Law (V = IR)
  • Knowledge of electromotive force (emf) concepts
  • Experience with voltmeter usage in circuits
NEXT STEPS
  • Study the principles of series and parallel circuits
  • Learn about the effects of resistance on circuit behavior
  • Explore the role of voltmeters in measuring voltage across components
  • Investigate the implications of circuit failure when components burn out
USEFUL FOR

Students studying electrical engineering, hobbyists working on circuit design, and educators teaching basic electronics concepts.

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Homework Statement




http://imageshack.us/m/508/9977/unlednia.png

The emf source resistance is equal to the bulb's resistance. The voltmeter has some big resistance and it shows 6volts.

What will the voltmeter show when the bulb burns out ?






Homework Equations



I think this is the equation needed : EMF=IR+Ir



The Attempt at a Solution



I don't know how to solve this please give a hint.
 
Last edited:
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EMF=IR+Ir
In the above equation it is given that r = R and IR = 6 V.
Then what is the EMF?
 
Last edited:
EMF=2IR=12V Thanks !
 

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