Solving Two Point Dipoles - Find Torque of p1 & p2

In summary, the problem given by Griffiths involves calculating the torque of two perpendicular point dipoles, p1 and p2, with a distance of r between them. The formula for the torque of a point dipole pointing in the z direction is given, and the solution for p1 can be easily calculated assuming it also points in the z direction. However, for p2, the axes can be rotated and the sum of the torques can be found using the conservation of angular momentum. There is a disagreement on whether rotating the axes will affect the results.
  • #1
Kolahal Bhattacharya
135
1

Homework Statement


Griffiths offers this problem: two point dipoles p1 and p2 are given.They are r distance away and they are perpendicular.We are asked to find torue of p1 (about p1's centre) due to p2 and vice versa.
Well, the situation is that I knoe it is =p cross E
even I know the formula for a point dipole pointing in the z direction:
E_dip=(1/(4*pi*epsilon))(p/r^3)[2cos(theta) (r^)+sin (theta) (theta^)
where (r^) and (theta^) are the unit vectors in a polar system coincident with the xyz system.
I can surely find the result for 1 part.Assuming p1 points in the z direction,it can be evaluated.What could be done in the second case?


Homework Equations





The Attempt at a Solution

 
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  • #2
Both torques are equally easy to compute. Just rotate your coordinate system. But you don't even have to. Their sum is the time rate of change of angular momentum, a conserved quantity. Think Newton's third law.
 
Last edited:
  • #3
You are WRONG.If I rotate the axes,the relative difference of answers will not be visible.
 
  • #4
Kolahal Bhattacharya said:
You are WRONG.If I rotate the axes,the relative difference of answers will not be visible.

Really? I have no idea what you mean to say, but I guess you know best.
 

Related to Solving Two Point Dipoles - Find Torque of p1 & p2

What is a two point dipole?

A two point dipole is a system consisting of two point charges with equal magnitude but opposite signs, separated by a distance d. It is commonly used to model the behavior of polar molecules and can also be used to study the behavior of electric fields.

What is torque?

Torque is a measure of the rotational force applied to an object. In the context of a two point dipole, it refers to the tendency of the dipole to rotate under the influence of an external electric field.

How do you find the torque of p1 and p2 in a two point dipole?

The torque of p1 and p2 in a two point dipole can be found using the equation T = p1 x E + p2 x E, where p1 and p2 are the magnitudes of the two point charges and E is the strength of the external electric field.

What factors affect the torque in a two point dipole?

The torque in a two point dipole is affected by the magnitude of the point charges, the distance between them, and the strength and direction of the external electric field.

How is the torque of a two point dipole related to its dipole moment?

The torque of a two point dipole is directly proportional to its dipole moment, which is the product of the magnitude of the point charges and the distance between them. This means that a larger dipole moment will result in a larger torque, and vice versa.

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