Hi again,
I was browsing for detailed info about induced emf and induced current in generators while found this interesting article :

I've found this page , with very good clear explanation :

https://www.cmm.gov.mo/eng/exhibition/secondfloor/moreinfo/2_4_1_ACGenerator.html

Except for one thing ,
the direction of induced currents on the image below :



------------------------------------------------------------------------------------------------------------
What about the direction of induced current?

Should we follow the right hand rule in determining direction of induced current?






-------------------------------------------------------------------------------------------------------------

Going Back to initial image :


Lets consider the "dark (grey)" conductor of the half-loop that is rotating inside the magnetic field

From 0 degree to 180 degree : "the grey" conductor is going in downward direction.



--->>>> If we follow right hand rule the direction of induced current should be exactly opposite to the direction, shown on the picture.




Found similar issues in many other sites.
Which is correct ?

Thank you.

 

You can use the right-hand corkscrew rule or the Right-Hand Rule to find:

1. the direction of the magnetic field from a current in a straight wire

1. the direction of the magnetic field in a solenoid

1. the direction of the force on a current-carrying wire in a magnetic field

For an electric generator, you need to observe Lenz's Law:

The direction of the electric current induced in a conductor by a changing magnetic field is such that the magnetic field
created by the induced current opposes changes in the initial magnetic field.

This follows from the law of conservation of energy, otherwise you would create perpetual motion (i.e. over unity).

In other words, use the Right-Hand Rule to find the force on the current-carrying wire. The force must oppose the motion of the generator, otherwise the generator would speed up.

My advise is, don't use the Left-Hand Rule because you will not remember when it applies. Use Lenz's Law instead.

 

Here is a quiz to see if you have gotten it right.

Imagine a cylindrical magnet falling inside a copper pipe.
In what direction is the induced eddy current?




Use the Right-Hand Rule and Lenz's Law to arrive at the answer.

This is an actual experiment used in a physics course on Electricity & Magnetism to demonstrate Lenz's Law.

 

So on this picture, the direction is not correct?
It should be opposite.

 

Looking at the 90° position, apply the Right-Hand Rule.
The direction of the force on the wire pushes against the direction of motion.
Hence this is correct.

 

Looking at the 90° position, apply the Right-Hand Rule.
The direction of the force on the wire pushes against the direction of motion.
Hence this is correct.

Sorry . For clarification, the picture is not correct

 

Sorry . For clarification, the picture is not correct

I don’t see a problem with the picture.

 

I don’t see a problem with the picture.

According to the attached picture, the direction of current should be opposite.

The Grey conductor.
Is going downwards direction
In the initial image

according RHR in the last picture the direction of current is not correct.

 

Go with the cross product of I x B.
The force F = I x B.
It appears that you are correct. The current direction is wrong.
I will review this later.

 

View attachment 367716

According to the attached picture, the direction of current should be opposite.

The Grey conductor.
Is going downwards direction
In the initial image

according RHR in the last picture the direction of current is not correct.

Correct current direction I guess
Please follow movements of grey conductor in the initial image


From 0 to 180 degrees.
In the last post the current directions are different

In both pictures the conductor is going downwards direction

 

One possible cause of confusion is whether the educational site is using conventional current flow or electron flow, though I have not encountered this.

Another confusion is the memory aid for how you label the digits on the hand. Some use the index finger to represent current direction. Then there is one rule for motors and the opposite for generators.

So, which one do we use?

In order to avoid confusion, use the right-hand corkscrew rule for the cross product.





The Lorentz Force is given by the cross product of positive charge flow times the magnetic field.

F = qv X B







This will determine the direction of the force for a motor.
Apply Lenz's law for a generator.

 

If I use this image

then initial current direction is wrong.

This is wrong





This is correct

 

The two drawings disagree with the direction of the current.
One of them is correct. Can you determine which one is correct?

 

Personally I think the initial image is wrong.
See Fleming Rhr for generator
See Fleming Lhr for motor
In Google.

Not confirmed 100 percent

 

Personally I think the initial image is wrong.
See Fleming Rhr for generator
See Fleming Lhr for motor
In Google.

Not confirmed 100 percent

The problem as I see it is, “which rule do you remember for a generator and which rule for a motor? ”

 

See Fleming Rhr for generator
See Fleming Lhr for motor

I guess is correct.

Other opinions are very welcomed.

 

See Fleming Rhr for generator
See Fleming Lhr for motor

I guess is correct.

Other opinions are very welcomed.

What I am asking, will you remember that rule?
Stick with the right hand rule for the Lorentz Force for force on a wire and use Lenz's Law for induced current.

 

Which one is correct?
This


or

This


Upper picture : Left conductor in downward direction

Down picture : Grey conductor is going downwards from 0 to 180 degrees

Which rule should I use ?
Thank you.

Maybe in post 19 I'll get a brief clear answer.

19 posts of questions to get a verified answer.

 

Hi again,
I was browsing for detailed info about induced emf and induced current in generators while found this interesting article :

I've found this page , with very good clear explanation :

https://www.cmm.gov.mo/eng/exhibition/secondfloor/moreinfo/2_4_1_ACGenerator.html

Except for one thing ,
the direction of induced currents on the image below :

View attachment 367699

------------------------------------------------------------------------------------------------------------
What about the direction of induced current?

Should we follow the right hand rule in determining direction of induced current?



View attachment 367700


-------------------------------------------------------------------------------------------------------------

Going Back to initial image :
View attachment 367701

Lets consider the "dark (grey)" conductor of the half-loop that is rotating inside the magnetic field

From 0 degree to 180 degree : "the grey" conductor is going in downward direction.



--->>>> If we follow right hand rule the direction of induced current should be exactly opposite to the direction, shown on the picture.




Found similar issues in many other sites.
Which is correct ?

Thank you.

Again. Is it correct or not ?
Thank you

 

I gave you the answer.
Did you not follow it?