Vector Functions with Zero Divergence and Curl

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Questions and Answers

Who is the author of the book 'Introduction to Electrodynamics'?

  • David J. Griffiths (correct)
  • Will Moore
  • Laura Kenney
  • Jim Smith

What is the edition of the book 'Introduction to Electrodynamics'?

  • Second Edition
  • Fourth Edition (correct)
  • Third Edition
  • Fifth Edition

Who is the Executive Editor of the book 'Introduction to Electrodynamics'?

  • Martha Steele
  • Jim Smith (correct)
  • Dorothy Cox
  • Laura Kenney

What is the publisher of the book 'Introduction to Electrodynamics'?

<p>Pearson Education, Inc. (C)</p> Signup and view all the answers

In which year was the book 'Introduction to Electrodynamics' copyrighted?

<p>All of the above (D)</p> Signup and view all the answers

What is the ISBN-10 of the book 'Introduction to Electrodynamics'?

<p>0-321-85656-2 (D)</p> Signup and view all the answers

Where is the permissions department of the publisher located?

<p>Glenview, IL 60025 (C)</p> Signup and view all the answers

What is the Library of Congress Cataloging-in-Publication Data number?

<ol> <li>Electrodynamics–Textbooks (C)</li> </ol> Signup and view all the answers

What is the dot product of x̂ and x̂?

<p>1 (B)</p> Signup and view all the answers

What is the result of multiplying a vector by a scalar?

<p>Each component is multiplied by the scalar (D)</p> Signup and view all the answers

What is the formula for the dot product of two vectors A and B?

<p>Ax Bx + Ay By + Az Bz (B)</p> Signup and view all the answers

What is the magnitude of a vector A?

<p>√(Ax^2 + Ay^2 + Az^2) (A)</p> Signup and view all the answers

What is the cross product of x̂ and ŷ?

<p>ẑ (C)</p> Signup and view all the answers

What is the formula for the cross product of two vectors A and B?

<p>(Ay Bz - Az By)x̂ + (Az Bx - Ax Bz)ŷ + (Ax By - Ay Bx)ẑ (A)</p> Signup and view all the answers

Why is the formula for the cross product written as a determinant?

<p>To make the formula more neat and compact (C)</p> Signup and view all the answers

What is the significance of the right-handed coordinate system?

<p>It is used exclusively in vector analysis (D)</p> Signup and view all the answers

What does the direction of the gradient ∇T represent?

<p>The direction of maximum increase of the function T (A)</p> Signup and view all the answers

What does the magnitude |∇T| represent?

<p>The rate of increase of the function T (A)</p> Signup and view all the answers

What is the direction of maximum descent?

<p>Opposite to the direction of maximum ascent (D)</p> Signup and view all the answers

What happens when θ = 0 in the equation dT = ∇T · dl = |∇T ||dl| cos θ?

<p>dT is maximum (C)</p> Signup and view all the answers

What does it mean for the gradient to vanish at a point?

<p>The function has a stationary point at that point (C)</p> Signup and view all the answers

What is the condition for the slope to be zero?

<p>θ = 90° (A)</p> Signup and view all the answers

What is a characteristic of surfaces that do not have the properties of the gradient?

<p>They are nondifferentiable (D)</p> Signup and view all the answers

In the context of the hill analogy, what does the function T represent?

<p>The height of the hill (B)</p> Signup and view all the answers

What is the derivative of (f + g) with respect to x?

<p>$\frac{df}{dx} + \frac{dg}{dx}$ (D)</p> Signup and view all the answers

What is the formula for the derivative of (k f) with respect to x?

<p>$k \frac{df}{dx}$ (B)</p> Signup and view all the answers

What is the primary limitation of Newtonian mechanics?

<p>Objects that are extremely small (A), Objects moving at high speeds (C)</p> Signup and view all the answers

What is the divergence of the sum of two vector fields A and B?

<p>$(∇ · A) + (∇ · B)$ (D)</p> Signup and view all the answers

What is the curl of the sum of two vector fields A and B?

<p>$(∇ × A) + (∇ × B)$ (A)</p> Signup and view all the answers

Who introduced special relativity in 1905?

<p>Albert Einstein (B)</p> Signup and view all the answers

What is the divergence of a vector field kA, where k is a constant?

<p>$k (∇ · A)$ (B)</p> Signup and view all the answers

What is the name of the mechanics that combines relativity and quantum principles?

<p>Quantum Field Theory (B)</p> Signup and view all the answers

What is the main focus of this book, excluding the last chapter?

<p>Classical Mechanics (A)</p> Signup and view all the answers

What is the curl of a vector field kA, where k is a constant?

<p>$k (∇ × A)$ (D)</p> Signup and view all the answers

What is a simple vector function that has zero divergence and zero curl?

<p>A constant vector field (A)</p> Signup and view all the answers

When was quantum mechanics developed?

<p>In the 1920s (B)</p> Signup and view all the answers

What is the formula for the derivative of (fg) with respect to x?

<p>$f \frac{dg}{dx} + g \frac{df}{dx}$ (A)</p> Signup and view all the answers

What is the primary concern of mechanics?

<p>How a system will behave when subjected to a given force (A)</p> Signup and view all the answers

Who contributed to the development of quantum mechanics?

<p>Niels Bohr, Erwin Schrödinger, and Heisenberg (A)</p> Signup and view all the answers

What is the name of the realm that deals with objects moving at high speeds?

<p>Special Relativity (D)</p> Signup and view all the answers

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Study Notes

Introduction to Electrodynamics

  • This is the fourth edition of the book, written by David J. Griffiths, with the copyright belonging to Pearson Education, Inc.

Four Realms of Mechanics

  • The four great realms of mechanics are:
    • Classical Mechanics (Newton)
    • Quantum Mechanics (Bohr, Heisenberg, Schrödinger, et al.)
    • Special Relativity (Einstein)
    • Quantum Field Theory (Dirac, Pauli, Feynman, et al.)
  • Newtonian mechanics is adequate for most purposes in everyday life, but it is incorrect for objects moving at high speeds (near the speed of light) and is replaced by special relativity, and for objects that are extremely small (near the size of atoms) it fails for different reasons and is superseded by quantum mechanics.
  • Quantum Field Theory combines relativity and quantum principles and is used for objects that are both very fast and very small.

Vector Analysis

  • Rule (i): To multiply a vector by a scalar, multiply each component by the scalar.
  • Rule (ii): To multiply by a scalar, multiply each component.
  • Rule (iii): To calculate the dot product, multiply like components, and add.
  • The dot product can be written as: A · B = Ax*Bx + Ay*By + Az*Bz
  • The magnitude of a vector can be calculated using the dot product: A = √(Ax^2 + Ay^2 + Az^2)
  • The cross product can be written as: A × B = (Ay*Bz - Az*By)x̂ + (Az*Bx - Ax*Bz)ŷ + (Ax*By - Ay*Bx)ẑ
  • The cross product can be written as a determinant: A × B = |x̂ ŷ ẑ| |Ax Ay Az|

Geometrical Interpretation of the Gradient

  • The gradient of a function points in the direction of maximum increase of the function.
  • The magnitude of the gradient gives the slope (rate of increase) along the maximal direction.
  • The direction of maximum descent is opposite to the direction of maximum ascent, while at right angles the slope is zero.
  • If the gradient vanishes at a point, then the function has a stationary point at that point.

Product Rules

  • The product rules for vector derivatives are similar to the rules for ordinary derivatives.
  • The sum rule: ∇(f + g) = ∇f + ∇g
  • The rule for multiplying by a constant: ∇(kf) = k∇f
  • The product rule is not as simple, but can be checked by the reader.

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