How Is the Formula PEcos(θ) Derived for Dipoles in a Constant Electric Field?

In summary, the potential energy of a dipole in a constant electric field can be calculated using the formula P(dot)E=PEcos(θ). To find this formula, one can use two charges of opposite signs located at the origin and at a given point, and then take the limit of the dipole moment as the distance between the charges approaches 0. This results in the formula V=-P(dot)E, which can be used to calculate the total potential energy of the dipole in the electric field.
  • #1
electrohau5
13
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I know that the potential energy of a dipole in a constant electric field is

P(dot)E=PEcos(θ), but I can't seem to find how they got here; its not in my textbook.

If anyone knows why please tell me.
 
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  • #2
A straight-forward way is to just use two charges of the same magnitude [itex]Q[/itex] and opposite sign located at the origin and at [itex]\vec{r}_0[/itex] (negative charge in the origin). The total potential energy of this charge distribution in the homogeneous electric field is
[tex]V=-Q \vec{r}_0 \cdot \vec{E}.[/tex]
Now the dipole moment is given for the limit [itex]\vec{r}_0 \rightarrow 0[/itex] such that [itex]Q \vec{r}_0=\vec{P}=\text{const}.[/itex] This leads to
[tex]V=-\vec{P} \cdot \vec{E}.[/tex]
QED.
 
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FAQ: How Is the Formula PEcos(θ) Derived for Dipoles in a Constant Electric Field?

What is the purpose of deriving PEcos(θ) for diploles in a constant electric field?

The derivation of PEcos(θ) for diploles in a constant electric field allows us to understand the energy interactions between a dipole and an external electric field. This is important in understanding the behavior and properties of polar molecules in the presence of an electric field.

How is PEcos(θ) for diploles in a constant electric field calculated?

The PEcos(θ) for diploles in a constant electric field is calculated by taking the dot product of the dipole moment vector and the electric field vector. This results in the potential energy of the dipole in the electric field.

What does the θ represent in the equation for PEcos(θ)?

The θ in the equation for PEcos(θ) represents the angle between the dipole moment vector and the electric field vector. This angle is important in determining the strength and direction of the potential energy of the dipole in the electric field.

How does the value of θ affect the potential energy of the dipole?

The value of θ affects the potential energy of the dipole in the electric field. When θ is 0 degrees, the dipole moment vector is parallel to the electric field vector, resulting in maximum potential energy. As θ increases, the potential energy decreases until it reaches 90 degrees, where the dipole moment vector is perpendicular to the electric field vector and the potential energy is 0.

What are some real-life applications of the derivation of PEcos(θ) for diploles in a constant electric field?

The derivation of PEcos(θ) for diploles in a constant electric field has various applications in fields such as chemistry, physics, and engineering. It is used to understand the behavior of polar molecules in an electric field, as well as in the design of devices such as capacitors and sensors. This understanding is also crucial in fields such as material science and nanotechnology.

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