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[SOLVED] Griffiths torque on a dipole
1. Homework Statement
This question refers to Griffiths E and M book.
In the sentence after equation 4.5, Griffiths says the following:
"For a perfect dipole of infinitesimal length, Eq 4.4 gives the torque about the center of the dipole..."
What is driving me insane is that I thought eqn 4.4 was true precisely when the dipole was finite since they say nothing about d being an infinitesimal there and the vector d sure does not look like an infinitesimal in Figure 4.5!?! I was sure that eqn 4.4 applied only for physical dipoles before I read that sentence! What is wrong here! Please help.
2. Homework Equations
3. The Attempt at a Solution
1. Homework Statement
This question refers to Griffiths E and M book.
In the sentence after equation 4.5, Griffiths says the following:
"For a perfect dipole of infinitesimal length, Eq 4.4 gives the torque about the center of the dipole..."
What is driving me insane is that I thought eqn 4.4 was true precisely when the dipole was finite since they say nothing about d being an infinitesimal there and the vector d sure does not look like an infinitesimal in Figure 4.5!?! I was sure that eqn 4.4 applied only for physical dipoles before I read that sentence! What is wrong here! Please help.
2. Homework Equations
3. The Attempt at a Solution