Past Paper Q's on Electromagnetic Breaking (1 Viewer)

[mtsmahia]

Hi Guys,

Ive been doing some past papers... and have noticed 2 different explanations that are given...

1)
an external magnetic field is applied to the conductive rotating disc. Due to the rotation, there is a change in flux and as a result of Lenz's Law, the magnetic field of the induced eddy currents will oppose the intial change in flux. The interaction of the both these magnetic fields will result in a force opposing the motion of the disc.

2) an external magnetic field is applied to the conductive rotating disc. Due to the rotation, there is a change in flux and as a result of Lenz's Law, the direction of the induced eddy currents are such that they oppose the motion of the disc. The portion of the eddy currents in the external magnetic field experience a force ( as a result of the motor effect) in the opposite direction of the disc's movement.

Which way should be used to explain?

 

[adomad]

National High Magnetic Field Laboratory Slideshow: Eddy Currents and Lenz's Law

they are the same, they are just wording lenz's law differently...

 

[study-freak]

1)
an external magnetic field is applied to the conductive rotating disc. Due to the rotation, there is a change in flux and as a result of Lenz's Law, the magnetic field of the induced eddy currents will oppose the intial change in flux. The interaction of the both these magnetic fields will result in a force opposing the motion of the disc.

2) an external magnetic field is applied to the conductive rotating disc. Due to the rotation, there is a change in flux and as a result of Lenz's Law, the direction of the induced eddy currents are such that they produce a magnetic field to oppose the original change in flux. The conductor with the portion of the eddy currents in the external magnetic field experience a force ( as a result of the motor effect) in the opposite direction of the disc's movement.

Can you see why the explanations were a bit different now?
I edited some parts of 2) to make it more detailed/correct.

 

[mtsmahia]

Thanks!!... but which explanation do u recommend to use in Exam's?

 

[study-freak]

Thanks!!... but which explanation do u recommend to use in Exam's?

I recommend my edited 2) lols

 

[mtsmahia]

I recommend my edited 2) lols

Ok lol... Thanks!!

 

[study-freak]

You're welcome!