Question about magnetic induction

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SUMMARY

This discussion centers on the principles of magnetic induction as applied to a current-carrying wire in a uniform magnetic field. The primary equation discussed is F = BIL, where F is the force, B is the magnetic field strength, I is the current, and L is the length of the wire. Participants clarify that when the wire moves, it induces an electromotive force (emf) that opposes the original current, leading to a state of equilibrium where the back emf equals the applied emf from the battery. The conversation highlights the importance of considering the area of the circuit and the presence of resistance in understanding the behavior of the induced current.

PREREQUISITES
  • Understanding of magnetic fields and forces (F = BIL)
  • Knowledge of electromotive force (emf) and back emf concepts
  • Familiarity with electric motor principles
  • Basic concepts of circuit resistance and its effects on current
NEXT STEPS
  • Study the principles of Faraday's Law of Electromagnetic Induction
  • Learn about the operation and design of electric motors
  • Explore the effects of resistance on induced emf in circuits
  • Investigate the relationship between magnetic flux and circuit area in induction scenarios
USEFUL FOR

Physics students, electrical engineers, and anyone interested in understanding the principles of magnetic induction and its applications in electric motors and circuits.

max11011
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hi everyone iam happy to join physics forums
i 'd like to ask a question about magnetic induction
if i have a current carrying wire(connected to a battery=V) of length (L)& of intensity (I) & perpendicular to a uniform magnetic field(B) then a force act on it (F=LIB)
so when it moves...if it changes the no. of magnetic field lines inside its circuit then it induces emf also a current which is oppostie to the one already passing in the circuit so the (F) decreases gradually until the induced emf become equal to the emf of the battery
so the final situation
Wire with no current (because of equilibrium that happened) moving with constant velocity...

is that right?...or i have missed something...
 
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welcome to pf!

hi max11011! welcome to pf! :smile:
max11011 said:
if i have a current carrying wire … perpendicular to a uniform magnetic field(B) then a force act on it (F=LIB)
so when it moves...if it changes the no. of magnetic field lines inside its circuit …

but why would it change the number of field lines (the magnetic flux)?

it's not rotating, and the field is uniform, so won't the lines cut ("cookie-cutter" style) stay the same? :confused:
 
Max: Yopu have picked up on 2 effects here
1) When a current carrying wire is placed in a magnetic field it experiences a force (BIL)
this is the principle behind the electric motor.
2) When a conductor moves through a magnetic field an emf is induced that opposes the change producing it. In an electric motor this is known as a 'back emf'
In an ideal case, with no energy losses, the motor will reach a speed where the back emf = the applied emf.
This does not mean the current will be zero ! If there are no energy losses it is possible to have a current with no resultant emf !
 
Thanks. ..tiny-tim for ur reply
but Although the field is uniform and no rotation...,the area of the circuit increases gradually so does the magnetic lines in the curcuit consequently...a current is indced.
The picture may make it more clear.

Thanks. ..truesearch...for ur reply...
so if the motor or the current carrying wire isn't ideal the back emf wouldn't equal forward emf.
 

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hi max11011! :wink:
max11011 said:
Thanks. ..tiny-tim for ur reply
but Although the field is uniform and no rotation...,the area of the circuit increases gradually so does the magnetic lines in the curcuit consequently...a current is indced.
The picture may make it more clear.

ah, yes, if the area is increasing :smile:

(btw, shouldn't "dots" be coming up towards us? :wink:)
 
If there is resistance in the circuit then the back emf will equal the supply emf -Ir.
This is the simplest case to consider when there is resistance present
 

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