Role of a voltmeter in an initially open circuit

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SUMMARY

The discussion centers on the role of a voltmeter in an open circuit scenario where the circuit is swung through a magnetic field. It is established that connecting a voltmeter across the open ends of the circuit effectively closes the circuit, allowing for measurement of electromotive force (emf). The debate revolves around the expected voltage readings, which can vary between two spikes (positive and negative) and a flat voltage graph, depending on the circuit's dynamics. The impact of the voltmeter on the circuit is influenced by its high input impedance, typically in the millions of Ohms, which minimizes current flow and thus affects the measurement.

PREREQUISITES
  • Understanding of electromotive force (emf) in circuits
  • Knowledge of magnetic fields and their interaction with conductors
  • Familiarity with voltmeter operation and impedance
  • Basic principles of circuit theory and measurement techniques
NEXT STEPS
  • Research the principles of electromagnetic induction and Faraday's Law
  • Explore the characteristics of high-impedance voltmeters and their applications
  • Learn about the effects of circuit loading on voltage measurements
  • Investigate graphical representations of voltage versus time in dynamic circuits
USEFUL FOR

Electronics students, electrical engineers, and anyone interested in understanding circuit behavior and measurement techniques in electromagnetic contexts.

justing943
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Hi!

Could someone briefly explain the following scenario to me please :)

If an open circuit (with the 2 ends named X and Y) hung on a string is swung through an into page magnetic field, what would the emf be? How would that change if you are asked about the voltage 'measured' between X and Y?

The answers that are debatable are between a graph where there are two spikes, one positive one negative, and a completely flat voltage graph.

If an open circuit is connected to a voltmeter (one end to each open end), how would that affect the circuit?

Thanks in advance :)
JT

edit: Sorry if this is in the wrong subforum (I suspect it belongs in the HW subforum)
 
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justing943 said:
Hi!

Could someone briefly explain the following scenario to me please :)

If an open circuit (with the 2 ends named X and Y) hung on a string is swung through an into page magnetic field, what would the emf be? How would that change if you are asked about the voltage 'measured' between X and Y?

The answers that are debatable are between a graph where there are two spikes, one positive one negative, and a completely flat voltage graph.

If an open circuit is connected to a voltmeter (one end to each open end), how would that affect the circuit?

Thanks in advance :)
JT

edit: Sorry if this is in the wrong subforum (I suspect it belongs in the HW subforum)
Hooking up a volt meter will close the circuit. A volt meter is actually measuring a current through a known impedance, but the scale is tuned into read voltage. However, the current is very low due to the high input impedance of the volt meter. So under "normal" conditions the current that flows through the volt meter is therfor not taken into account. Modern volt meters is controlled by an electronic circuit that has a few million Ohms input impedance.

How much the volt meter affect the circuit will therefor depend on the voltmeter properties and the circuit that is measured.

Vidar
 
Thanks very much for the reply :). I do believe that solves my problem :D
 

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