# Magnitude and Direction of induced voltage

## Homework Statement

Hey everyone I have a physics e&m question: [/B]
http://blob:https%3A//www.physicsforums.com/aa779f37-be23-43d7-a888-d70263a3854b ## The Attempt at a Solution I took the derivative to find the magnitude of the induced voltage. (do I need to add a constant c?)
I am having trouble with the direction of the current flow though... Do I use the right hand rule?

Thanks![/B]

## Answers and Replies

Simon Bridge
Science Advisor
Homework Helper
I took the derivative to find the magnitude of the induced voltage. (do I need to add a constant c?)
I am having trouble with the direction of the current flow though... Do I use the right hand rule?
The constant "c" is usually either the speed of light in a vacuum or the constant of integration ... do either of these situation apply here?
The current flow is determined by the right hand rule in conjunction with a law of physics that applies to induced currents.
I'm puzzled you started at (c) ... did you do (a) and (b)?

andrevdh
Homework Helper
4 a) Does the question ask for the magnetic (flux) ?

Oh, it should read the magnitude, not magnetic!

Shouldn't you use Faraday's law?

andrevdh
Homework Helper
There might be a small gap in the lower right-hand part of the loop

• Simon Bridge
Simon Bridge
Science Advisor
Homework Helper
Well spotted - there may well be.

Sorry! Yeah I meant magnitude.

Last edited:
Okay so the derivative of magnetic flux is the induced voltage. I am having trouble calculating flux. Flux = BA cos (theta). How do I get the area....?

Simon Bridge
Science Advisor
Homework Helper
What shape is the area in question?

Ahh I forgot that they gave us the length of the square. I think I was able to get it. Does this look right?

Simon Bridge
Science Advisor
Homework Helper
in (c) and (d) the flux density is different in different parts of the square, how did you account for this?
(hint: the variable y should not be in your answer)
in (b) the question asks for the direction of the current

For b) I say it is counterclockwise. My reasoning is that the field is decreasing as time passes (e^(-t)). The field will want to come out and the way to do that is for the induced current to flow counterclockwise.

I am not clear on c). Doesn't the y variable account for the different flux values for different y values?