Confused about j hat in this magnetic field problem.

In summary, when finding the force on a point particle with a charge of -3.64 nC and a velocity of 2.75 x 10^3 m/s i in a magnetic field of 0.75 Ti + 0.75 Tk, one must use the formula F=qv x B. The solution manual may show a positive number, but this is due to the negative sign of the charge. One must also remember that negative charges will move in the opposite direction of positive charges.
  • #1
charlies1902
162
0

Homework Statement


A point particle has a charge equal to –3.64 nC and a velocity equal to
2.75 10^3 m/s i. Find the force on the charge if the magnetic field is
(d) 0.75 Ti + .75Tk

The solution manual had a positive number. I thought it was a typo until I saw the next problem where they got the opposite sign of what I got again for j hat.
F=qv x B, how is it possible that they got a + #?
 
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  • #2
I think that i x k = -j, just as you do. However, another negative sign enters into the equation by means of q, which is intrinsically negative here. Negative charges will move in the opposite direction of positive charges.
 
  • #3
cepheid said:
I think that i x k = -j, just as you do. However, another negative sign enters into the equation by means of q, which is intrinsically negative here. Negative charges will move in the opposite direction of positive charges.
OMG I'm so stupid I completely forgot about that, been too long since I did cross products. thanks a lot
 

1. What is j hat in a magnetic field problem?

J hat, or ȷ̂, is a unit vector that represents the direction of the current flow in a magnetic field problem. It is typically used in vector notation to indicate the direction and magnitude of the current.

2. How is j hat related to the magnetic field?

J hat is related to the magnetic field through the cross product of the current and the magnetic field vectors. It represents the direction of the magnetic force on a charged particle moving through the magnetic field.

3. Why is j hat important in solving magnetic field problems?

J hat is important in solving magnetic field problems because it helps define the direction of the current and the resulting magnetic force. It is a crucial component in understanding the behavior of charged particles in magnetic fields.

4. How do I determine the direction of j hat in a magnetic field problem?

The direction of j hat can be determined through the right-hand rule, where the fingers of your right hand point in the direction of the current and your thumb points in the direction of the magnetic field. The direction of j hat is then perpendicular to both the current and the magnetic field.

5. Can j hat ever change direction in a magnetic field problem?

No, j hat does not change direction in a magnetic field problem. It remains perpendicular to both the current and the magnetic field, unless there are external forces acting on the charged particles.

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