How to find speed with Faraday's law

AI Thread Summary
The discussion centers on calculating the force required to move a metal rod at a constant speed in a magnetic field and determining the work dissipated in a resistor after the rod is released. The relevant formula for force is given as F=IBl, where the magnetic field B is 1T, the distance d is 0.1m, and resistance R is 0.1 ohm. Participants emphasize the importance of understanding the relationship between the rod's motion and the change in magnetic flux, which affects the induced electromotive force. There is a request for a diagram to better visualize the problem, and some confusion remains regarding the calculation of the change in area as the rod moves. Overall, the conversation aims to clarify the application of Faraday's law in this scenario.
Jacobs
Messages
8
Reaction score
0

Homework Statement


A metal rod can slide on a rail without any friction in the presence of uniform magnetic field of B=1T which is perpendicular to the plane of the paper.The distance between the tracks is d=0.1m and the resistance given is R=0.1 ohm.The resistance of the rail is negligible and the mass of the rod is m=20g. A)How much force must be on the road exerted in order to move it with a constant speed of v=10m/s? B)The rod has been moved for t=2s and then it is released.How much work is dissioated on the resistor till the rop will stop?

Homework Equations


F=IBl=B^2*l^2*v/R

The Attempt at a Solution


According to first formula F=1 but for B i have no idea
 
Last edited:
Physics news on Phys.org
Welcome to the PF.

Could you please post the figure that goes with this question? It sounds like a classic sliding rail changing the total B*dA, but it's hard for me to be sure from the text of your post. Thanks. :smile:
 
1st one
 

Attachments

  • 4d155cb0-ea4b-44ff-9a13-c96cc8a43e82.jpg
    4d155cb0-ea4b-44ff-9a13-c96cc8a43e82.jpg
    18.7 KB · Views: 453
You might start here. http://hyperphysics.phy-astr.gsu.edu/hbase/electric/farlaw.html

The rails and the rod and resistor make an electric loop. You can find the area of that loop if you know the length, but for this problem, you are interested in the Change in the area when the rod moves. Since Phi = B*A, phi can change if B changes or (in your case) when A changes. It doesn't do a whole lot of good to have some formulas, unless you have an idea of where they come from. Then you'll understand which ones to use.
 
so formula is BdeltaA/delta(t) but still have no idea about how find find change in the area
 
Answer of B is 2?
 
Jacobs said:
so formula is BdeltaA/delta(t) but still have no idea about how find find change in the area
The motion of the movable rod changes the area.
Jacobs said:
Answer of B is 2?
Please always show your detailed work so we can check it. Thank you.
 
  • Like
Likes scottdave

Similar threads

Making sense of sequence of ideas in MIT OCW's 8.02 notes on Faraday
Replies
1
Views
1K
Understanding the math of definition of electromotive force
Replies
1
Views
984
How does an eddy current brake work exactly?
Replies
2
Views
2K
Induced EMF and current for a bar sliding on a circular rail
Replies
22
Views
3K
Rod on rails in a magnetic field
Replies
5
Views
2K
Faraday's Law: Induced Voltage and Current in a Loop with Resistance R
Replies
3
Views
2K
Lenz's Law and Faraday's Law clarification
Replies
11
Views
2K
Faraday's Law - loop turning in the Earth's B-field
Replies
9
Views
2K
Faraday's law and linearly time dependent B field
Replies
3
Views
1K
Why Are My Calculations for Current in Moving Rods Using the Blv Rule Incorrect?
Replies
2
Views
1K

Hot Threads

Recent Insights

Back
Top