/*! 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 9 How would you position a flat lo... [FREE SOLUTION] | 91Ó°ÊÓ

91Ó°ÊÓ

How would you position a flat loop of wire in a changing magnetic field so that there is no induced emf in the loop?

Short Answer

Expert verified
To position the flat loop of wire in a changing magnetic field such that there is no induced emf, the angle between the magnetic field and the normal (perpendicular) to the plane of the loop should be either parallel (angle \(θ = 0\)°) or antiparallel (angle \(θ = 180\)°). In these cases, the magnetic flux will be constant and not change with time, ensuring no induced emf.

Step by step solution

01

Understand Faraday's Law

Faraday's law states that the induced electromotive force (emf) in a closed loop of wire is equal to the negative rate of change of the magnetic flux through the loop. Mathematically, this is represented as: \(emf = -\frac{dΦ}{dt}\) Where \(emf\) is the induced electromotive force, \(Φ\) is the magnetic flux, and \(t\) is the time.
02

Determine the magnetic flux

The magnetic flux, \(Φ\), through a loop is given by the product of the magnetic field strength (\(B\)), the area of the loop (\(A\)), and the cosine of the angle (\(θ\)) between the magnetic field and the normal (perpendicular) to the plane of the loop: \(Φ = B × A × cos(θ)\) Where \(0\) \(≤ θ ≤ 180°\).
03

Set the condition for no induced emf

Since we want no induced emf, the rate of change of magnetic flux with respect to time should be zero. From Faraday's law, we have: \(-\frac{dΦ}{dt} = 0\) Taking the derivative of the flux equation with respect to time will give us the condition for zero induced emf: \(\frac{d(B × A × cos(θ))}{dt} = 0\)
04

Analyze the possible cases

There are three cases to consider: 1. The magnetic field strength (\(B\)) is constant: If the magnetic field strength is constant, the loop orientation won't matter since the rate of change of magnetic flux with respect to time is zero in this case. 2. The area of the loop (\(A\)) is constant: If the area of the loop is constant, it still depends on the magnetic field and the angle between the field and the loop. 3. The angle between magnetic field and loop normal (\(θ\)) is constant: If the angle is constant, it still depends on the magnetic field and the area of the loop. In order to cancel the induced emf, we need to find the case that makes the magnetic flux independent of time.
05

Position the loop to eliminate induced emf

The only way to ensure that the magnetic flux is independent of time is to position the loop so that the angle \(θ\) between the magnetic field and the normal to the plane of the loop is either \(0\)° (parallel) or \(180\)° (antiparallel). In these cases, the cosine function will equal either 1 or -1, and the magnetic flux will be constant (not changing with time) regardless of any time-varying magnetic field strength: \(cos(0) = 1\) \(cos(180) = -1\) So, to position the flat loop of wire in a changing magnetic field such that there is no induced emf, the angle between the magnetic field and the normal (perpendicular) to the plane of the loop should be either parallel (angle \(θ = 0\)°) or antiparallel (angle \(θ = 180\)°).

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.

Over 30 million students worldwide already upgrade their learning with 91Ó°ÊÓ!

Key Concepts

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

Induced EMF
Induced Electromotive Force (EMF) is an important concept from Faraday's law that describes how a voltage is generated in a circuit. Specifically, this occurs when there is a change in magnetic flux through the loop. The key equation from Faraday's law is \( emf = -\frac{d\Phi}{dt} \). Here, \( emf \) denotes the induced EMF, and \( \Phi \) represents the magnetic flux. The minus sign in the equation indicates Lenz’s law, which tells us that the induced EMF will always oppose the change in flux that produced it. If the magnetic flux is changing rapidly, a large EMF is induced. If it's steady, no EMF is induced. This principle is used widely, such as in electric generators and induction cooktops. Understanding induced EMF helps in comprehending how electricity can be generated from changing magnetic fields. When the alignment of a circuit and the magnetic field is optimized, as explained in the exercise, you can eliminate or maximize the induced EMF.
Magnetic Flux
Magnetic Flux is the measure of the quantity of magnetism, considering the strength and the extent of a magnetic field. It can be thought of as the number of magnetic field lines passing through a given area. Mathematically, magnetic flux \( \Phi \) is calculated using the formula: \( \Phi = B \times A \times \cos(\theta) \). Here, \( B \) is the magnetic field strength, \( A \) is the area through which the field lines penetrate, and \( \theta \) is the angle between the field lines and the normal to the surface.- **Flux is proportional to the field strength.** Greater the magnetic field, the more flux passes through a given area.- **Flux is affected by the surface area.** A bigger loop or surface allows more field lines to pass through, so the total flux increases.- **Flux depends on orientation.** When the angle is \(0^{\circ}\) (normal to the surface), maximum flux occurs. When \(\theta = 90^{\circ}\), no field lines pass through perpendicularly, minimizing flux.For zero induced EMF, we want a situation where magnetic flux is constant over time, meaning no change in \( \Phi \). As the step-by-step solution demonstrates, achieving this involves orientation manipulation.
Magnetic Field Orientation
The orientation of the magnetic field in relation to the loop is crucial in determining how much magnetic flux passes through and whether an EMF is induced. By adjusting the angle between the magnetic field and the normal to the loop's plane, we can influence the effectiveness at which the magnetic field penetrates the area.- **Maximum alignment occurs when \( \theta = 0^{\circ} \)**, meaning the magnetic field lines are perfectly perpendicular to the surface. This is when the flux is maximal and changes most efficiently with any field variation, leading to high EMF potential.- **Inverse alignment is at \( \theta = 180^{\circ} \).** Despite being on opposite sides, the field lines penetrate with equal effectiveness, maintaining a potential for significant change in flux if field strength alters.To avoid any EMF being induced, however, the magnetic flux must remain unchanged over time. As the original exercise describes, achieving this by setting the loop at these orientations means any changes in the field do not result in fluctuation of magnetically linked lines through the loop. Consequently, positioning the loop this way ensures zero induced EMF, preventing any electrical current from being generated.

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 bar magnet falls under the influence of gravity along the axis of a long copper tube. If air resistance is negligible, will there be a force to oppose the descent of the magnet? If so, will the magnet reach a terminal velocity?

A 0.50-kg copper sheet drops through a uniform horizontal magnetic field of \(1.5 \mathrm{T}\), and it reaches a terminal velocity of \(2.0 \mathrm{m} / \mathrm{s}\). (a) What is the net magnetic force on the sheet after it reaches terminal velocity? (b) Describe the mechanism responsible for this force. (c) How much power is dissipated as Joule heating while the sheet moves at terminal velocity?

A metal bar of mass \(m\) slides without friction over two rails a distance \(D\) apart in the region that has a uniform magnetic field of magnitude \(B_{0}\) and direction perpendicular to the rails (see below). The two rails are connected at one end to a resistor whose resistance is much larger than the resistance of the rails and the bar. The bar is given an initial speed of \(v_{0} .\) It is found to slow down. How far does the bar go before coming to rest? Assume that the magnetic field of the induced current is negligible compared to \(B_{0}\).

Design a current loop that, when rotated in a uniform magnetic field of strength 0.10 T, will produce an emf \(\varepsilon=\varepsilon_{0} \sin \omega t, \quad\) where \(\varepsilon_{0}=110 \mathrm{V}\) and \(\omega=120 \pi \mathrm{rad} / \mathrm{s}\).

A circular copper disk of radius \(7.5 \mathrm{cm}\) rotates at 2400 rpm around the axis through its center and perpendicular to its face. The disk is in a uniform magnetic field \(\overrightarrow{\mathbf{B}}\) of strength \(1.2 \mathrm{T}\) that is directed along the axis. What is the potential difference between the rim and the axis of the disk?

See all solutions

Recommended explanations on Physics Textbooks

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.