Is the term loop loosely defined in Faraday's law?

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The term "loop" in Faraday's law refers to a closed path through which magnetic field flux can change, inducing voltage. A voltage can still be induced even if the loop is open, as demonstrated with a voice coil microphone, where relative motion between the coil and magnet is necessary for voltage fluctuations. The discussion highlights that voltage is measured between two points, raising questions about defining "ends" in a circular loop. It is clarified that while a closed loop typically results in a smaller voltage and larger current, an open loop can still generate voltage. The conversation also touches on the differences between dynamic and electret microphones in terms of their operation and requirements.
LightFantastic
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Is the term "loop" loosely defined in Faraday's law?

A voltage will be induced in a loop of wire when the magnetic field flux through the loop changes

If you're reading this, you probably know what happens when you hook up the leads from an oscilloscope to a microphone. Nothing, lol. There needs to be relative motion between the voicecoil and the permanent magnet for you to view any voltage fluctuations.And here is the origin of my confusion,

Disconnect the leads. The voicecoil is now open ended. In other words, it is NO LONGER a true loop. Will a voltage still be induced? Also, voltage is a measure between two points or ends in the case of a voice coil. How am I supposed to find the "ends" in a circle?
 
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You mean - does the loop have to be closed?
No.
 
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Without the loop closed there will be a voltage and current induced in the loop. By the way, the scope is a very high input impedance and having it connected is very close to having the loop open. With the loop closed, the voltage around the loop gets smaller and the current gets bigger. The voltage around the loop is defined for a specific path. If we start at point A, go around the loop once and end on the same point, there is a definite voltage along that path.

Claude
 
LightFantastic said:
A voltage will be induced in a loop of wire when the magnetic field flux through the loop changes

If you're reading this, you probably know what happens when you hook up the leads from an oscilloscope to a microphone. Nothing, lol. There needs to be relative motion between the voicecoil and the permanent magnet for you to view any voltage fluctuations.And here is the origin of my confusion,

Disconnect the leads. The voicecoil is now open ended. In other words, it is NO LONGER a true loop. Will a voltage still be induced? Also, voltage is a measure between two points or ends in the case of a voice coil. How am I supposed to find the "ends" in a circle?

Using a moving coil "dynamic" microphone, you should get an output if you talk into it and this may be visible on the oscilloscope trace if you have enough gain in the oscilloscope.

These microphones are now fairly rare and you might be using an "electret" microphone which requires a source of DC voltage to make it work.
 

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