- #1
Jonnie79
- 2
- 0
My question is at the bottom of this post
PREAMBLE:
If a dipole is turned by an angle θ (in a uniform electric field) then the torque applied on the dipole by the electric field will be:
τ = 2.q.a.E.sin(-θ) = -2.q.a.E.sin(θ)
with the negative sign referring to it being a "restoring" torque. This negative sign is important in:
-dU = ∫τ.dθ = -2.q.a.E.∫sin(θ).dθ
IN TERMS OF VECTORS:
In τ = p x E
p = 2.q.a (in the direction of a), and
E.sin(θ) is the "x E" part of τ = p x E
MY QUESTION:
Where is the negative sign gone in the vector equation? what accounts for it?
PREAMBLE:
If a dipole is turned by an angle θ (in a uniform electric field) then the torque applied on the dipole by the electric field will be:
τ = 2.q.a.E.sin(-θ) = -2.q.a.E.sin(θ)
with the negative sign referring to it being a "restoring" torque. This negative sign is important in:
-dU = ∫τ.dθ = -2.q.a.E.∫sin(θ).dθ
IN TERMS OF VECTORS:
In τ = p x E
p = 2.q.a (in the direction of a), and
E.sin(θ) is the "x E" part of τ = p x E
MY QUESTION:
Where is the negative sign gone in the vector equation? what accounts for it?
Last edited: