What would the voltmeters measure?

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Homework Help Overview

The discussion revolves around the measurement of voltage in a scenario involving a conducting rod and induced electromotive force (emf). Participants are exploring the relationship between the induced emf and the readings of voltmeters in a specific setup.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants are questioning the validity of the assertion that the induced emf is the same for both voltmeters. There is a focus on understanding the implications of the rod's conductivity and resistance in the circuit.

Discussion Status

The discussion is active, with participants challenging initial claims and seeking clarification on the principles involved, such as the Lorentz force. There is an exploration of how the characteristics of the circuit affect the voltage readings.

Contextual Notes

Participants note the importance of the rod's conductivity and the resistance of the U-shaped loop, indicating that these factors are critical to understanding the voltage measurements. There is an acknowledgment of the complexity involved in formulating meaningful physics problems.

JACKR
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Homework Statement
I made up this problem and it is not a homework.

The tale goes like this: A rod moving with a constant speed towards the left on a U-shaped conductor in a uniform magnetic field B that is directed into the page. The width of the U-shaped conductor is L and the length of the rod is L'. V1 is connected across the part of the rod making contact with U-shaped conductor thus completing the circuit, whereas V2 is connected across the whole rod. The voltmeters are assumed co-planar with the rod as far as we're concerned and are held in a plane perpendicular to it.
Relevant Equations
ε=∮(v̅×B̅)•dl̅=-dΦ/dt
I am saying that V1=V2 since the emf induced in the rod is the same for both cases equal BLv. Am I correct?

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No
 
BvU said:
No
Why not?
 
JACKR said:
the emf induced in the rod is the same for both cases equal BLv
is not correct
 
BvU said:
is not correct
Yep, Why isn't it correct?
 
BvU said:
Are you familiar with the Lorentz force ?

##\ ##
Ofcourse
 
You forgot to mention the rod is conducting...
And that its resistance is zero ...
And the U-shaped loop also has resistance zero ...
(composing meaningful exercises isn't as simple as it seems :smile:)

So what does ##V_1## read ? Zero or BLv ?
##V_2## reads 2 B(L'-L)v more

##\ ##
 
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