/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 61 Find an expression for the oscil... [FREE SOLUTION] | 91Ó°ÊÓ

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Find an expression for the oscillation frequency of an electric dipole of dipole moment \(\vec{p}\) and rotational inertia \(I\) for small amplitudes of oscillation about its equilibrium position in a uniform electric field of magnitude \(E\).

Short Answer

Expert verified
The oscillation frequency is \( \omega = \sqrt{\frac{pE}{I}} \).

Step by step solution

01

Understand the Physical Situation

An electric dipole in an external electric field experiences a torque, given by \( \vec{\tau} = \vec{p} \times \vec{E} \). For small displacements from equilibrium, this torque will result in oscillatory motion around the equilibrium position.
02

Write the Torque Equation for Small Angles

For small angles \( \theta \), the torque can be approximated as \( \tau = pE \sin \theta \approx pE \theta \), where \( \theta \) is the angular displacement from equilibrium.
03

Apply Newton's Second Law for Rotation

Newton's second law for rotational motion is \( I \alpha = \tau \), where \( \alpha \) is the angular acceleration. Substituting the torque gives us \( I \frac{d^2\theta}{dt^2} = -pE \theta \).
04

Form the Simple Harmonic Motion Equation

The differential equation \( I \frac{d^2\theta}{dt^2} = -pE \theta \) is of the form \( \frac{d^2\theta}{dt^2} = -\omega^2 \theta \), which is the standard form for simple harmonic motion with \( \omega^2 = \frac{pE}{I} \).
05

Solve for Angular Frequency

From \( \omega^2 = \frac{pE}{I} \), we have \( \omega = \sqrt{\frac{pE}{I}} \). The angular frequency \( \omega \) is the rate of oscillation around the equilibrium.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Electric Dipole
An electric dipole consists of two equal and opposite charges separated by a small distance. It is characterized by a dipole moment, denoted as \( \vec{p} \). This vector points from the negative charge to the positive charge and has a magnitude equal to the charge multiplied by the separation distance. Electric dipoles tend to align with an external electric field. This happens because the positive and negative charges experience forces in opposite directions within the field, causing a torque. Important aspects of an electric dipole:
  • Alignment with electric fields due to torque.
  • Oscillatory motion when displaced from equilibrium.
  • Defined by a dipole moment \( \vec{p} \).
These properties are crucial for understanding how dipoles behave in external fields and how they can undergo oscillation.
Rotational Inertia
Rotational inertia, or moment of inertia, \( I \), is a measure of an object's resistance to change in its rotational motion. It is analogous to mass in linear motion. Every object has a unique rotational inertia based on its mass distribution relative to the axis of rotation. In the context of an electric dipole, the rotational inertia affects how easily the dipole can oscillate. The larger the rotational inertia, the more difficult it is to change the dipole's rotational state.Key points about rotational inertia:
  • Depends on mass distribution relative to axis of rotation.
  • Larger values indicate greater resistance to rotational change.
  • Crucial in determining oscillation frequency of a dipole.
By understanding rotational inertia, we can better predict the behavior of rotating systems, like our electric dipole in an electric field.
Small Amplitude Oscillations
Small amplitude oscillations refer to oscillations where the displacement from the equilibrium position is very small. This allows us to make certain mathematical approximations, such as using linear terms instead of trigonometric functions.In classical mechanics, small amplitude oscillations often result in simple harmonic motion (SHM), which is described by:\[ I \frac{d^2\theta}{dt^2} = -pE \theta\]This equation arises from the assumption that sine functions can be approximated by their angles when the angles are small. Thus, the motion is simplified and behaves predictably.Significant aspects:
  • Linear approximation for simple calculations.
  • Predictable motion pattern (SHM).
  • Found in many physical systems where oscillations occur.
Recognizing small amplitude oscillations is helpful in modeling the behavior of systems experiencing periodic motion.
Uniform Electric Field
A uniform electric field is one where the electric field strength is constant in both magnitude and direction throughout a given space. This means that an electric dipole placed in such a field will experience the same force at every point within the field. In the case of an electric dipole, this uniform field can cause the dipole to experience consistent torque, leading to oscillations. The predictability and uniformity make calculations around electric dipoles more straightforward. Characteristics of a uniform electric field:
  • Constant field strength across the field.
  • Consistent force on charged particles.
  • Influential in determining dipole behavior.
Understanding uniform electric fields allows for easier prediction of charged particle interactions, like those found in electric dipoles.

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Most popular questions from this chapter

Beams of high-speed protons can be produced in "guns" using electric fields to accelerate the protons. (a) What acceleration would a proton experience if the gun's electric field were \(2.00 \times 10^{4} \mathrm{~N} / \mathrm{C} ?\) (b) What speed would the proton attain if the field accelerated the proton through a distance of \(1.00 \mathrm{~cm} ?\)

The following table gives the charge seen by Millikan at different times on a single drop in his experiment. From the data, calculate the elementary charge \(e\). $$ \begin{array}{lll} \hline 6.563 \times 10^{-19} \mathrm{C} & 13.13 \times 10^{-19} \mathrm{C} & 19.71 \times 10^{-19} \mathrm{C} \\ 8.204 \times 10^{-19} \mathrm{C} & 16.48 \times 10^{-19} \mathrm{C} & 22.89 \times 10^{-19} \mathrm{C} \\ 11.50 \times 10^{-19} \mathrm{C} & 18.08 \times 10^{-19} \mathrm{C} & 26.13 \times 10^{-19} \mathrm{C} \\ \hline \end{array} $$

An electron with a speed of \(5.00 \times 10^{8} \mathrm{~cm} / \mathrm{s}\) enters an electric field of magnitude \(1.00 \times 10^{3} \mathrm{~N} / \mathrm{C}\), traveling along a field line in the direction that retards its motion. (a) How far will the electron travel in the field before stopping momentarily, and (b) how much time will have elapsed? (c) If the region containing the electric field is \(8.00 \mathrm{~mm}\) long (too short for the electron to stop within it), what fraction of the electron's initial kinetic energy will be lost in that region?

(a) What is the magnitude of an electron's acceleration in a uniform electric field of magnitude \(1.40 \times 10^{6} \mathrm{~N} / \mathrm{C} ?\) (b) How long would the electron take, starting from rest, to attain one-tenth the speed of light? (c) How far would it travel in that time?

Two particles, each of positive charge \(q\), are fixed in place on a \(y\) axis, one at \(y=d\) and the other at \(y=-d\). (a) Write an expression that gives the magnitude \(E\) of the net electric field at points on the \(x\) axis given by \(x=\alpha d\). (b) Graph \(E\) versus \(\alpha\) for the range \(0<\) \(\alpha<4\). From the graph, determine the values of \(\alpha\) that give (c) the maximum value of \(E\) and \((\mathrm{d})\) half the maximum value of \(E .\)

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