Log out Go to App
Go to App

Learning Materials

Features

Discover

Chapter 20: Q73P (page 863)

A bar magnet whose magnetic dipole moment is 15 A.m2is aligned with an applied magnetic field of 4 T. How much work must you do to rotate the bar magnet 180°to point in the direction opposite to the magnetic field?

Short Answer

Expert verified

The work done to rotate the bar magnet 180°to point in the direction opposite to the magnetic field is 120 J.

Step by step solution

01

Given Information

The dipole moment of the magnet is μ=15 A.m2, and the magnetic field is B=4 T. T. The bar rotates at an angle θ=180°.

02

Work done

The directions of the bar rotation and the magnetic torque are the same, therefore, the work done is non-zero and equals to the difference between the two potential energies at the angle θ1=0and θ2=180°given as:

W=ΔU2−ΔU1                      ⋯1

Where the potential energy for a magnetic dipole is given by

U=−μ→⋅B→=−μBcosθ

Therefore, the equation can be written as:

W=ΔU1−ΔU2=−μBcosθ2−−μBcosθ1=μBcosθ1−cosθ2                       ⋯2

03

Calculate the work done

Substitute the given values of μ,B,θ1and θ2into equation (2) to get the work done.

W=μBcosθ1−cosθ2=15⋅4cos0°−cos180°=601−−1=120 J

Thus, the work done is 120 J.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Start your free trial

Over 30 million students worldwide already upgrade their learning with Vaia!

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

A neutral iron bar is dragged to the left at speed v through a region with a magnetic field B points out of the page (Figure 20.122). Which diagram (1-5) best shows the state of the bar?

Calculate the mobile electron density for nickel. A mole of nickel has a mass of 59g (0.059kg), and one mobile electron is released by each atom in metallic nickel. The density of nickel is about 8.8g/cm3, or8.8×103kg/m3

You hold your magnet perpendicular to a bar of copper that is connected to a battery (Figure 20.84). Describe the directions of the components of the electric field at the center of the copper bar, both parallel to the bar and perpendicular to the bar. Explain carefully.

Explain briefly why there is a limit to how much charge can be placed on a metal sphere in the classroom. If the radius of the sphere is 15 cm what is the maximum amount of charge you can place on the sphere? (Remember that a uniform sphere of charge makes an electric field outside the sphere as though all the charge were concentrated at the center of the sphere.)

A copper wire with square cross section carries a conventional current I to the left (as in Figure 20.83). There is a magnetic field B perpendicular to the wire. Describe the direction of E⊥, the transverse electric field inside the wire due to the Hall effect, and explain briefly.
See all solutions

Recommended explanations on Physics Textbooks

Force

Read Explanation

Turning Points in Physics

Read Explanation

Physical Quantities And Units

Read Explanation

Circular Motion and Gravitation

Read Explanation

Medical Physics

Read Explanation

Waves Physics

Read Explanation
View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.

Sign-up for free