/*! 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 Two coils have the same number o... [FREE SOLUTION] | 91Ó°ÊÓ

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Two coils have the same number of circular turns and carry the same current. Each rotates in a magnetic field as in Figure 21.19 . Coil 1 has a radius of \(5.0 \mathrm{cm}\) and rotates in a \(0.18-\mathrm{T}\) field. Coil 2 rotates in a \(0.42-\mathrm{T}\) field. Each coil experiences the same maximum torque. What is the radius (in \(\mathrm{cm}\) ) of coil \(2 ?\)

Short Answer

Expert verified
The radius of coil 2 is approximately 3.27 cm.

Step by step solution

01

Identify Given Values

Coil 1 has a radius \( r_1 = 5.0 \) cm and rotates in a magnetic field \( B_1 = 0.18 \) T. Coil 2 rotates in a magnetic field \( B_2 = 0.42 \) T, and the maximum torque for both coils is the same.
02

Understand Torque Formula

The torque \( \tau \) on a coil in a magnetic field is given by \( \tau = nIAB \sin(\theta) \), where \( n \) is the number of turns, \( I \) is the current, \( A \) is the area of the coil, and \( \theta \) is the angle between the normal to the coil and the magnetic field. At maximum torque, \( \sin(\theta) = 1 \). So, \( \tau = nIAB \).
03

Set Torque Equality for Coils

For the two coils to experience the same maximum torque, we have \( nI \pi r_1^2 B_1 = nI \pi r_2^2 B_2 \). Since \( n \) and \( I \) are the same for both coils, they can be canceled from the equation.
04

Simplify and Solve

Cancel out the common terms and simplify the equation to get \( r_1^2 B_1 = r_2^2 B_2 \). Rearrange this to find \( r_2^2 = \frac{r_1^2 B_1}{B_2} \).
05

Calculate Radius of Coil 2

Substitute the known values: \( r_1 = 5.0 \) cm, \( B_1 = 0.18 \) T, and \( B_2 = 0.42 \) T, into the equation: \( r_2^2 = \frac{(5.0^2) \times 0.18}{0.42} \). Calculate \( r_2 = \sqrt{\frac{25 \times 0.18}{0.42}} \).
06

Complete the Calculation

Evaluate the expression: \( r_2 = \sqrt{\frac{4.5}{0.42}} \). This simplifies to \( r_2 \approx \sqrt{10.714} \approx 3.27 \) cm.

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Key Concepts

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

Circular Coil
A circular coil is a loop or series of loops made out of wire that is arranged in a circular shape. It plays a critical role in electromagnetic applications, such as generating magnetic fields or interacting with them. - Circular coils can have one or more loops, commonly referred to as 'turns.' - The main motif for their use is the uniformity of the magnetic field they can create at the center. - In this context, two identical circular coils are used with the same number of turns and current, providing a baseline to study their interaction with magnetic fields. The interaction with magnetic fields results in phenomena like torque, which is what causes a coil to rotate or experience a twisting force.
Radius Calculation
When solving for the radius of a coil that produces the same torque as another coil, certain calculations are involved. Here, you begin with the torque formula and manipulate it algebraically to find the unknown radius:1. Start with setting the torques equal for two coils experiencing the same forces.2. Cancel out common factors, such as the number of turns and current, simplifying the equation.3. The resulting equation involves the radii squared and the magnetic fields: \( r_1^2 B_1 = r_2^2 B_2 \).4. Rearrange to focus on the unknown radius: \( r_2^2 = \frac{r_1^2 B_1}{B_2} \).By substituting the given values and calculating, you find the radius of the second coil. This is crucial to maintain the relationship that dictates equal torque, even in differing magnetic environments.
Magnetic Field Strength
Magnetic field strength, represented by the symbol \( B \), is a measure of the magnetic force in a given area. It is crucial in determining how much torque a coil will experience when placed in that field. The unit of magnetic field strength is the Tesla (\( T \)).- A stronger magnetic field (higher \( B \) value) will typically result in a larger force on an object within it.- In the exercise, coil 1 has a weaker field than coil 2, with \( B_1 = 0.18 \) T and \( B_2 = 0.42 \) T. By understanding and using these magnetic field strengths, you determine how manipulating other variables like coil radius will allow both coils to experience the same amount of torque.
Torque Equation
The torque equation is pivotal in understanding how a coil behaves in a magnetic field. Torque, symbolized by \( \tau \), refers to the rotational force experienced by the coil.- The fundamental equation is \( \tau = nIAB \sin(\theta) \).- At maximum torque, \( \sin(\theta) = 1 \), simplifying the equation to \( \tau = nIAB \).This highlights the dependency on:- Number of turns (\( n \)).- Current (\( I \)).- Area of the coil (\( A \)), which is linked to its radius: \( A = \pi r^2 \).- Magnetic field strength (\( B \)).By setting the torques equal for both coils (\( \tau_1 = \tau_2 \)), we unravel the mathematical derivation for the coil radius, crucial in maintaining identical rotational impacts despite differing magnetic fields.

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Most popular questions from this chapter

A \(45-\mathrm{m}\) length of wire is stretched horizontally between two vertical posts. The wire carries a current of \(75 \mathrm{A}\) and experiences a magnetic force of \(0.15 \mathrm{N} .\) Find the magnitude of the earth's magnetic field at the location of the wire, assuming the field makes an angle of \(60.0^{\circ}\) with respect to the wire.

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