Motional emf, Gaussian flux, and lenz's law help

1. Apr 11, 2012

Turpulus

1. The problem statement, all variables and given/known data

Two bars, each 30cm long, and each having a resistance of 2-ohms, are connected to a 1,500 volt battery. The bars are attached to each other with 3 insulating springs, each having a spring constant of 9N/m. The two bars are initially at rest, 4cm apart. The switch is closed, and then opened. Assume no friction anywhere in the system. 1. How far will the two bars be from each other with the switch is closed? 2. After the switch is open, what is the closest the two bars wil get to eachother? 3. After the switch is open, what is the farthest the two bars will get from each other? 4. Describe the motion of the two bars at time, t, after the switch is open.

2. Relevant equations

v ir
Spring constant equations

3. The attempt at a solution

I know motional emf would cause the bars to move apart but they're not passing through a magnetic field. Are they generating a mag field? Are they acting as capacitors and building up repulsive charges? If so, how do you get the area of the bar if you are only given the length? Thanks!!

2. Apr 11, 2012

issacnewton

Hi, is there a diagram given ? without the aid of a diagram its difficult to understand.
Always post the question AS IT APPEARS in your text book or homework......

3. Apr 12, 2012

Turpulus

Here is the exact question with diagram:
Two bars, each 30cm long, and each having a resistance of 2.00 ohms, are connected to a 1500V battery. The bars are attached to each other with 3 insulating springs each having a spring constant of 9N/m. The two bars are initially at reast, 4cm apart. The switch is closed, and then opened. Assume there is no friction anywhere in the system. Note: One can define the equivalent srping constant for the system equal to 27N/m. 1. How far will the two bars be from each other with the switch closed? 2. After the switch is open, what is the closest the two bars will get to each other? 3. After the switch is open, what is the farthest the two bars will get from each other. 4. Describe the motion of the two bars at time, t, after the switch is open.

So I realize that the bars are connected in parallel, so the equivalent resistance is 1ohm. I'll post a diagram.

4. Apr 12, 2012

Turpulus

Here is the diagram. Thanks!!

File size:
66.2 KB
Views:
62