• Support PF! Buy your school textbooks, materials and every day products via PF Here!

EMF induced in rotating rod inside uniform magnetic field

  • Thread starter songoku
  • Start date
1,177
23
1. Homework Statement
A 40 cm rod is rotated about its centre inside a region of uniform magnetic field of 6.4 T. Given that the speed of rotation is 15 rad/s, find potential difference between the centre and either end of the rod

2. Homework Equations
emf = - ΔΦ / Δt

ω = 2π / T

3. The Attempt at a Solution
emf = - B cos θ . ΔA / Δt = - B . πr2 / T

I just need to plug the numbers with r = 20 cm (because from center to either end of rod)?

Thanks
 

Delta2

Homework Helper
Insights Author
Gold Member
2,384
668
In one full period T, the radius of the rod which is ##r=20cm## (since ##d=40cm## is the diameter) covers a surface of a full circle which is ##\pi r^2##. You can use the diameter but then you ll have to take the formula ##\pi\frac{d^2}{4}## for the surface of the circle.
 
Last edited:
1,177
23
In one full period T, the radius of the rod which is ##r=20cm## (since ##d=40cm## is the diameter) covers a surface of a full circle which is ##\pi r^2##. You can use the diameter but then you ll have to take the formula ##\pi\frac{d^2}{4}## for the surface of the circle.
For the time, do I use the period because half of the rod travels full circle in one full period or I use half of period because one whole rod covers one full circle in half period?

Thanks
 

Delta2

Homework Helper
Insights Author
Gold Member
2,384
668
For the time, do I use the period because half of the rod travels full circle in one full period or I use half of period because one whole rod covers one full circle in half period?

Thanks
You use the full period for half rod, otherwise if you follow the 2nd approach you find the EMF between the two ends of the rod. But the problem asks for the EMF between one end and the center, that's why we have to take the area that the half rod covers in one full period.
 
1,177
23
You use the full period for half rod, otherwise if you follow the 2nd approach you find the EMF between the two ends of the rod. But the problem asks for the EMF between one end and the center, that's why we have to take the area that the half rod covers in one full period.
If the question asks the emf between two ends of the rod, will the answer be zero because they have the same value and the difference = 0?

Thanks
 

Delta2

Homework Helper
Insights Author
Gold Member
2,384
668
If the question asks the emf between two ends of the rod, will the answer be zero because they have the same value and the difference = 0?

Thanks
Yes, the emf between the two ends is zero.
 
1,177
23
Thank you very much
 

Want to reply to this thread?

"EMF induced in rotating rod inside uniform magnetic field" You must log in or register to reply here.

Related Threads for: EMF induced in rotating rod inside uniform magnetic field

Replies
33
Views
9K
Replies
6
Views
271
  • Posted
Replies
13
Views
4K
  • Posted
Replies
1
Views
2K
  • Posted
Replies
1
Views
12K
Replies
1
Views
5K

Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving
Top