/*! 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 59 A very long insulating cylinder ... [FREE SOLUTION] | 91Ó°ÊÓ

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A very long insulating cylinder with radius \(R_{\text {cylinder }}\) has nonuniform positive charge density \(\rho=\left(1-r / R_{\text {cylinder }}\right) \rho_{0}\) where \(\rho_{0}\) is constant and \(r\) is measured radially from the axis of the cylinder. A particle with charge \(-Q\) and mass \(M\) orbits the cylinder at a constant distance \(R_{\text {orbit }}>R_{\text {cylinder }}\) (a) What is the linear charge density \(\lambda\) of the tube, in terms of \(R_{\text {cylinder }}\) and \(\rho_{0} ?\) (b) Determine the period of the motion in terms of \(R_{\text {orbit }}\) (Hint: Use Gauss's law to determine the electric field, and therefore the electric force felt by the particle, that acts centripetally.)

Short Answer

Expert verified
The linear charge density \( \lambda \) of the cylinder and the period \( T \) of the particle's motion need to be calculated specifically for the given parameters. They can be found by integrating over the volume of the cylinder for \( \lambda \) and by applying Gauss's Law for \( T \).

Step by step solution

01

Calculate the Linear Charge Density

To calculate the linear charge density, we need to integrate over the volume of the cylinder to determine the total charge. The cylinder with charge per volume \( \rho = (1 - r / R_{cylinder}) \rho_0 \) varies linearly with the radius. We express the infinitesimal volume for cylindrical coordinates \( dv = r dr d\phi dz \). Then, the total charge \( Q \) becomes: \[ Q = \int_{0}^{R_{cylinder}} \int_{0}^{2\pi} \int_{0}^{L} \rho r dr d\phi dz \] where \( L \) is the length of the cylinder. We complete the integration to find \( Q \). The linear charge density \( \lambda \), which is total charge over the length, becomes: \[ \lambda = \frac{Q}{L} \].
02

Calculation of The Electric Field

To calculate the electric field, we use Gauss's Law. Shrinking the Gaussian surface to just contain the charged cylinder (with radius \( R_{orbit} \)), we can write Gauss's Law as: \[ E 2\pi R_{cylinder} L = \frac{Q}{\epsilon_0} \] From here, we solve for the electric field \( E \).
03

Determine the Centripetal Force on Particle

The centripetal force that keeps the particle in circular orbit is the force of the electric field \( E \) acting on it. This force is given by \( F = EQ \). As this is equal to the centripetal force \( F = \frac{MV^2}{R_{orbit}} \) where \( M \) is the mass of the particle and \( V \) is the orbital speed, we can equate the two expressions to find \( V \).
04

Calculate the Period of The Particle's Motion

The period \( T \) of the orbital motion is the time it takes for one complete revolution, or the circumference of the orbit divided by the speed \( V \). We can express the period of motion as: \[ T = \frac{2\pi R_{o}}{V} \] Calculate \( T \) using the previously found value of \( V \).

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Key Concepts

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

Gauss's Law
In the context of a cylindrical charge distribution, Gauss's Law is crucial for determining the electric field generated by the charge. Gauss's Law states that the total electric flux through a closed surface is equal to the charge enclosed by that surface divided by the permittivity of free space, \( \epsilon_0 \).

Mathematically, it is represented as \( \Phi_E = \oint_S \vec{E} \cdot d\vec{A} = \frac{q_{\text{enc}}}{\epsilon_0} \), where \( \Phi_E \) is the electric flux, \( \vec{E} \) is the electric field, \( d\vec{A} \) is the differential area vector of the closed surface 'S', and \( q_{\text{enc}} \) is the charge enclosed. By applying this principle, we can simplify complex charge distributions to calculate the electric field at a point in space, especially if the charge distribution exhibits symmetry such as cylindrical symmetry.
Electric Field
Understanding electric fields produced by charge distributions is fundamental for analyzing forces on charged particles. An electric field at a point in space represents the force per unit charge if a positive test charge were placed at that point. For the given exercise, we apply Gauss's Law to compute the electric field outside a non-uniformly charged cylinder.

By creating an imaginary Gaussian surface, specifically a cylindrical shell encompassing the charged cylinder and at distance \( R_{\text{orbit}} > R_{\text{cylinder}} \), one can calculate the electric field pushed by the charges inside this Gaussian surface. Since the electric field is directed radially outward, it provides the centripetal force necessary for the negative charged particle to remain in orbit.
Centripetal Force
Centripetal force is the inward-directed force that is required for an object to move in a circular path. In this problem, the centripetal force is the result of the electric field acting on the charged particle, keeping it in circular motion around the cylinder. The magnitude of this force can be calculated by \( F_{\text{centripetal}} = \frac{MV^2}{R_{\text{orbit}}} \), where 'M' is the mass of the particle, 'V' is its orbital velocity, and \( R_{\text{orbit}} \) is the radius of the orbit.

The electric force acting on the particle due to the cylinder's charge distribution provides the required centripetal force for orbital motion, demonstrating a fascinating interplay between electrostatics and motion.
Orbital Period
The orbital period is the time taken for a charged particle to complete one orbit around the cylindrical charge distribution. It is a direct measure of the orbital motion's frequency. From a physics standpoint, understanding the orbital period is essential for predicting the behavior of a particle under the influence of an electromagnetic field.

In the scenario described in the exercise, once the orbiting velocity has been calculated using the balance of electric and centripetal forces, the orbital period, \( T \) can be found with \( T = \frac{2\pi R_{\text{orbit}}}{V} \). This relationship implies that the period depends on the size of the orbit and the velocity of the particle. Consequently, a full understanding of the orbital period contributes to a comprehensive grasp of the dynamics involved in electromechanical systems where charge distributions influence motion patterns.

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Most popular questions from this chapter

A very long, solid insulating cylinder has radius \(R\); bored along its entire length is a cylindrical hole with radius \(a\). The axis of the hole is a distance \(b\) from the axis of the cylinder, where \(a

A uniformly charged insulating sphere with radius \(r\) and charge \(+Q\) lies at the center of a thin-walled hollow cylinder with radius \(R>r\) and length \(L>2 r\). The cylinder is non-conducting and carries no net charge. (a) Determine the outward electric flux through the rounded "side" of the cylinder, excluding the circular end caps. (Hint: Choose a cylindrical coordinate system with the axis of the cylinder as its \(z\) -axis and the center of the charged sphere as its origin. Note that an area element on the cylinder has magnitude \(d A=2 \pi R d z .\) ) (b) Determine the electric flux upward through the circular cap at the top of the cylinder. (c) Determine the electric flux downward through the circular cap at the bottom of the cylinder. (d) Add the results from parts (a)-(c) to determine the outward electric flux through the closed cylinder. (e) Show that your result is consistent with Gauss's law.

A solid conducting sphere carrying charge \(q\) has radius \(a\). It is inside a concentric hollow conducting sphere with inner radius \(b\) and outer radius \(c .\) The hollow sphere has no net charge. (a) Derive expressions for the electric-field magnitude in terms of the distance \(r\) from the center for the regions \(rc .\) (b) Graph the magnitude of the electric field as a function of \(r\) from \(r=0\) to \(r=2 c\). (c) What is the charge on the inner surface of the hollow sphere? (d) On the outer surface? (e) Represent the charge of the small sphere by four plus signs. Sketch the field lines of the system within a spherical volume of radius \(2 c\).

Which statement is true about \(\overrightarrow{\boldsymbol{E}}\) inside a negatively charged sphere as described here? (a) It points from the center of the sphere to the surface and is largest at the center. (b) It points from the surface to the center of the sphere and is largest at the surface. (c) It is zero. (d) It is constant but not zero.

An electron is released from rest at a distance of \(0.300 \mathrm{~m}\) from a large insulating sheet of charge that has uniform surface charge density \(+2.90 \times 10^{-12} \mathrm{C} / \mathrm{m}^{2}\). (a) How much work is done on the electron by the electric field of the sheet as the electron moves from its initial position to a point \(0.050 \mathrm{~m}\) from the sheet? (b) What is the speed of the electron when it is \(0.050 \mathrm{~m}\) from the sheet?

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