/*! 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 42 Figure \(30-56\) shows a copper ... [FREE SOLUTION] | 91Ó°ÊÓ

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Figure \(30-56\) shows a copper strip of width \(W=16.0 \mathrm{~cm}\) that has been bent to form a shape that consists of a tube of radius \(R=1.8 \mathrm{~cm}\) plus two parallel flat extensions. Current \(i=35 \mathrm{~mA}\) is distributed uniformly across the width so that the tube is effectively a one-turn solenoid. Assume that the magnetic field outside the tube is negligible and the field inside the tube is uniform. What are (a) the magnetic field magnitude inside the tube and (b) the inductance of the tube (excluding the flat extensions)?

Short Answer

Expert verified
(a) Magnetic field magnitude is approximately \(3.88 \times 10^{-4} \text{ T}\). (b) Inductance is approximately \(1.02 \times 10^{-9} \text{ H}\).

Step by step solution

01

Understand Biot-Savart Law for Solenoids

The magnetic field \[ B = \frac{\mu_0 n i}{L} \]where \( \mu_0 \) is the permeability of free space \(4\pi \times 10^{-7} \text{ Tm/A} \), \( n \) is the number of turns per unit length, \( i \) is the current, and \( L \) is the length of the solenoid.
02

Derive number of turns per unit length

Since the tube is a one-turn solenoid, we define it as having one turn over the length of its circumference. The circumference \( C \) of the tube is given by \( C = 2\pi R \). Therefore, the number of turns per unit length \( n = \frac{1}{C} = \frac{1}{2\pi R} \).
03

Calculate Magnetic Field (Part a)

Substitute the values into the magnetic field equation:\[B = \frac{\mu_0 i}{2\pi R}\]For \( R = 0.018 \text{ m} \) and \( i = 35 \times 10^{-3} \text{ A} \), we calculate:\[B = \frac{4\pi \times 10^{-7} \times 35 \times 10^{-3}}{2\pi \times 0.018}\approx 3.88 \times 10^{-4} \text{ T}\]
04

Understand Inductance Formula

The inductance of a solenoid is given by:\[ L = \frac{\mu_0 n^2 A}{L} \]where \( A \) is the cross-sectional area of the solenoid. Since it's a one-turn solenoid, we modify it for single length around the circumference.
05

Calculate Inductance (Part b)

The inductance of the tube for one turn can be simplified to:\[ L = \frac{\mu_0 A}{2\pi R}\]The cross-sectional area \( A \) is \( \pi R^2 \). Substitute the known values:\[L = \frac{4\pi \times 10^{-7} \pi \times (0.018)^2}{2\pi \times 0.018}\approx 1.02 \times 10^{-9} \text{ H}\]

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Key Concepts

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

Biot-Savart Law
The Biot-Savart Law allows us to determine the magnetic field generated by a current-carrying conductor. It's an essential tool in electromagnetism, written as:\[ B = \frac{\mu_0 n i}{L} \]This equation is particularly useful for solenoids—a type of electromagnet. Here, \( B \) is the magnetic field, \( \mu_0 \) is the magnetic permeability of free space (approximately \( 4\pi \times 10^{-7} \text{ Tm/A} \)), \( n \) represents the number of turns per unit length, \( i \) is the current through the solenoid, and \( L \) is its length.For solenoids, the field inside is considered uniform and concentrated alongside the axis of the tube. This makes them highly effective in applications where a stable magnetic field is needed. By understanding the Biot-Savart Law, we can precisely calculate how the solenoid's dimensions and current influence its magnetic strength. By applying the law to the one-turn solenoid in our problem, we derive a simple and effective expression for its magnetic field.
Inductance
Inductance depicts a solenoid's ability to store energy within its magnetic field, when current flows through it. The formula generally used is:\[ L = \frac{\mu_0 n^2 A}{L} \]Here, \( L \) is the inductance, \( A \) is the cross-sectional area of the solenoid, and the other symbols retain their prior meanings.In the context of a one-turn solenoid, modifications simplify the inductance calculation. Since the solenoid has only one turn, the squared term \( n^2 \) becomes irrelevant, and the expression adjusts to account for the solenoid's unique structure over its circumferential length.Understanding inductance helps us predict how the solenoid responds to changes in current. In particular, it defines the energy retention capacity of the solenoid's magnetic field, a key feature in many electrical applications like transformers and inductors.
Solenoid Formulas
Solenoids are fascinating because of their simple yet powerful ability to generate uniform magnetic fields. Key formulas that capture their properties include the expressions for magnetic field and inductance.For the magnetic field in solenoids, we use:\[ B = \frac{\mu_0 i}{2\pi R} \]This accounts for the one-turn configuration of the solenoid in our problem. The circumference serves as its effective length, providing a straightforward pathway for the current.For inductance, we've modified the standard formula:\[ L = \frac{\mu_0 \pi R^2}{2\pi R} \]These formulations elegantly tie together the concept of turns, cross-sectional area, and dimensions in producing and controlling magnetic effects efficiently. Understanding these formulas enforces a deeper appreciation of design strategies employed in engineering applications where controlled magnetic fields are necessary.
Magnetic Field Calculation
Calculating the magnetic field produced by a solenoid involves precision and understanding of the underlying principles. For a one-turn solenoid, we make use of:\[ B = \frac{\mu_0 i}{2\pi R} \]Here, \( R \) stands for the radius of the tube. This equation simplifies the calculation since the problem specifies the current runs uniformly across the solenoid's circumference—resulting in a condensed form of the Biot-Savart Law.By plugging in the given values—\( R = 0.018 \text{ m} \) and \( i = 35 \times 10^{-3} \text{ A} \)—we find the magnetic field inside the tube is approximately \( 3.88 \times 10^{-4} \text{ T} \). This exercise showcases how the magnetic field's magnitude is influenced by the solenoid's dimensions and the current it carries.Such calculations are a cornerstone in designing and understanding devices that utilize electromagnetism, from medical imaging equipment like MRI machines to everyday devices in electronics.

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Most popular questions from this chapter

Two coils are at fixed locations. When coil 1 has no current and the current in coil 2 increases at the rate \(15.0 \mathrm{~A} / \mathrm{s}\), the emf in coil 1 is \(25.0 \mathrm{mV}\). (a) What is their mutual inductance? (b) When coil 2 has no current and coil 1 has a current of \(3.60 \mathrm{~A}\), what is the flux linkage in coil \(2 ?\)

A coil with 150 turns has a magnetic flux of \(50.0 \mathrm{nT} \cdot \mathrm{m}^{2}\) through each turn when the current is \(2.00 \mathrm{~mA}\). (a) What is the inductance of the coil? What are the (b) inductance and (c) flux through each turn when the current is increased to \(4.00 \mathrm{~mA}\) ? (d) What is the maximum emf \(\mathscr{E}\) across the coil when the current through it is given by \(i=(3.00 \mathrm{~mA}) \cos (377 t)\), with \(t\) in seconds?

Assume that \(\mathscr{E}=10.0 \mathrm{~V}\), \(R=6.70 \Omega\), and \(L=5.50 \mathrm{H}\). The ideal battery is connected at time \(t=0\). (a) How much energy is delivered by the battery during the first \(2.00 \mathrm{~s}\) ? (b) How much of this energy is stored in the magnetic field of the inductor? (c) How much of this energy is dissipated in the resistor?

An electric generator contains a coil of 100 turns of wire, each forming a rectangular loop \(50.0 \mathrm{~cm}\) by \(30.0 \mathrm{~cm}\). The coil is placed entirely in a uniform magnetic field with magnitude \(B=\) \(3.50 \mathrm{~T}\) and with \(\vec{B}\) initially perpendicular to the coil's plane. What is the maximum value of the emf produced when the coil is spun at 1000 rev/min about an axis perpendicular to \(\vec{B}\) ?

A coil is connected in series with a \(10.0 \mathrm{k} \Omega\) resistor. An ideal \(50.0 \mathrm{~V}\) battery is applied across the two devices, and the current reaches a value of \(2.00 \mathrm{~m}\) A after \(5.00 \mathrm{~ms}\). (a) Find the inductance of the coil. (b) How much energy is stored in the coil at this same moment?

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