Force on a metal bar across two wires in a magnetic field

In summary, the problem involves finding the relationship between F = ma and F = -IlB. The current is induced by the changing magnetic flux and the potential difference across the capacitor is related to the emf. Neglecting electrical resistance, the Blv law may be used instead of Faraday's law for finding the emf in moving media.
  • #1
aolivias
1
0
Homework Statement
two parallel wires. The distance between the wires is d from each other and they are connected by a capacitor with the capacitance C. The constant magnetic field B is applied and is perpendicular to the plane of the wires. We put a metallic bar across the parallel wires and start pulling it with force F parallel to the wires. What is the acceleration of the bar?
Relevant Equations
I also attached my work to a file so it can be readable. I also did it here below:

I so far did C=Q/V,
I=dQ/dt,
I=c*dV/dt
F=ma, F=-IlB. I set these equations equal to each other:
ma=-IlB, In the next step I substituted c*dV/dt for I and got:
m*dv/dt=-(cdVlb)/dt
then, I substituted a into dv/dt and solved for a and then for final answer:
a=-(cvlb)/(mt)

I am not sure if this is correct or if I am on the right path.
I need help with the problem above
 

Attachments

  • Capacitance.pdf
    504.9 KB · Views: 229
Physics news on Phys.org
  • #2
aolivias said:
F=ma, F=-IlB. I set these equations equal to each other
F = ma should be written as ∑F = ma. The left side is the vector sum of the forces acting on the bar.
The force Fmag = IlB is the magnitude of the magnetic force acting on the bar. But there is also the applied force, F, acting on the bar.

The current is produced by the induced emf, ε, due to the changing magnetic flux through the circuit. So, you will need to bring in Faraday's law of induction. How is ε related to the potential difference, V, across the capacitor?

The problem statement is not clear. I guess you are meant to neglect any electrical resistance in the wires and in the bar.
 
Last edited:
  • #3
aolivias said:
I need help with the problem above
I agree with post 2 except when it comes to moving media I prefer the Blv law (l=distance, v=velocity) to faraday's law for finding the emf. You can get into trouble with faraday's law in moving media. The Blv law is based on the Lorentz force which has a different basis than faraday's.

Otherwise, just play with the various relations as post 2 suggests.
 

1. What is the force on a metal bar in a magnetic field?

The force on a metal bar in a magnetic field is known as the Lorentz force. It is the force exerted on a charged particle moving through a magnetic field. This force is perpendicular to both the direction of the magnetic field and the direction of motion of the particle.

2. How is the force on a metal bar in a magnetic field calculated?

The force on a metal bar in a magnetic field can be calculated using the formula F = qvBsinθ, where q is the charge of the particle, v is its velocity, B is the strength of the magnetic field, and θ is the angle between the direction of motion and the direction of the magnetic field.

3. What is the direction of the force on a metal bar in a magnetic field?

The direction of the force on a metal bar in a magnetic field is always perpendicular to both the direction of the magnetic field and the direction of motion of the particle. This means that the force will either be pushing or pulling the particle in a direction that is perpendicular to its original motion.

4. How does the length of the metal bar affect the force in a magnetic field?

The length of the metal bar does not directly affect the force in a magnetic field. However, the longer the bar, the greater the distance the charged particles travel through the magnetic field, which can result in a greater force being exerted on the bar.

5. Can the force on a metal bar in a magnetic field be controlled?

Yes, the force on a metal bar in a magnetic field can be controlled by changing the strength or direction of the magnetic field, or by altering the velocity or charge of the particles moving through the field. This allows for precise manipulation of the metal bar's movement and position.

Similar threads

  • Introductory Physics Homework Help
Replies
7
Views
1K
  • Introductory Physics Homework Help
Replies
6
Views
372
  • Introductory Physics Homework Help
Replies
16
Views
406
  • Introductory Physics Homework Help
Replies
8
Views
435
  • Introductory Physics Homework Help
Replies
1
Views
222
  • Introductory Physics Homework Help
Replies
14
Views
1K
Replies
2
Views
89
  • Introductory Physics Homework Help
Replies
1
Views
360
  • Introductory Physics Homework Help
Replies
1
Views
328
  • Introductory Physics Homework Help
Replies
5
Views
229
Back
Top