/*! 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 22 Determine whether the following ... [FREE SOLUTION] | 91Ó°ÊÓ

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Determine whether the following vector fields are conservative on the specified region. If so, determine a potential function. Let \(R^{*}\) and \(D^{*}\) be open regions of \(\mathbb{R}^{2}\) and \(\mathbb{R}^{3}\), respectively, that do not include the origin. $$\mathbf{F}=\langle y z, x z, x y\rangle \text { on } \mathbb{R}^{3}$$

Short Answer

Expert verified
The given vector field is conservative on the specified region of \(\mathbb{R}^{3}\), and the potential function is \(\phi(x, y, z) = xyz\).

Step by step solution

01

Calculate the curl of the given vector field

The curl of a vector field \(\mathbf{F} = \langle F_1, F_2, F_3 \rangle\) can be calculated using the following determinant involving partial derivatives: $$ \nabla \times \mathbf{F} = \left\langle \frac{\partial F_3}{\partial y} - \frac{\partial F_2}{\partial z}, \frac{\partial F_1}{\partial z} - \frac{\partial F_3}{\partial x}, \frac{\partial F_2}{\partial x} - \frac{\partial F_1}{\partial y} \right\rangle $$ For our given vector field, \(\mathbf{F} = \langle y z, x z, x y \rangle\). Let's compute the curl for our vector field: $$ \nabla \times \mathbf{F} = \left\langle \frac{\partial (x y)}{\partial y} - \frac{\partial (x z)}{\partial z}, \frac{\partial (y z)}{\partial z} - \frac{\partial (x y)}{\partial x}, \frac{\partial (x z)}{\partial x} - \frac{\partial (y z)}{\partial y} \right\rangle = \left\langle x - x, y - y, z - z \right\rangle $$ So we have \(\nabla \times \mathbf{F} = \left\langle 0, 0, 0 \right\rangle\).
02

Determine if the vector field is conservative

Since the curl of the vector field is zero, i.e., \(\nabla \times \mathbf{F} = \left\langle 0, 0, 0 \right\rangle\), the vector field is conservative on the specified region of \(\mathbb{R}^{3}\).
03

Find a potential function

To find the potential function, we need to solve the following equations for a scalar function \(\phi(x, y, z)\): 1. \(\frac{\partial \phi}{\partial x} = yz\) 2. \(\frac{\partial \phi}{\partial y} = xz\) 3. \(\frac{\partial \phi}{\partial z} = xy\) Now, integrate each equation with respect to their respective variables. 1. Integrating equation (1) with respect to \(x\): \(\phi(x, y, z) = \int yz \, dx = xyz + g(y, z)\) 2. Integrating equation (2) with respect to \(y\): \(\phi(x, y, z) = \int xz \, dy = xyz + h(x, z)\) 3. Integrating equation (3) with respect to \(z\): \(\phi(x, y, z) = \int xy \, dz = xyz + k(x, y)\) Notice that we get the same term \(xyz\) when we integrate each equation. Let's combine these results: $$ \phi(x, y, z) = xyz + g(y, z) + h(x, z) + k(x, y) $$ From this equation, we see that \(g(y,z) = 0\), \(h(x,z)= 0\), and \(k(x,y) = 0\). Thus, the potential function is given by: $$ \phi(x, y, z) = xyz $$ We have determined that the vector field is conservative and the potential function is \(\phi(x, y, z) = xyz\).

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Key Concepts

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

Curl of a Vector Field
The concept of the **curl** of a vector field is fundamental in vector calculus. It provides a measure of the rotational motion in a field, capturing how the field "curls" around a point. Whenever you have a vector field \( \mathbf{F} = \langle F_1, F_2, F_3 \rangle \), the curl \( abla \times \mathbf{F} \) is determined by calculating partial derivatives and setting them into a cross product-like structure:\[abla \times \mathbf{F} = \left\langle \frac{\partial F_3}{\partial y} - \frac{\partial F_2}{\partial z}, \frac{\partial F_1}{\partial z} - \frac{\partial F_3}{\partial x}, \frac{\partial F_2}{\partial x} - \frac{\partial F_1}{\partial y} \right\rangle\]If the curl evaluates to zero, as it did in our vector field \( \mathbf{F} = \langle yz, xz, xy \rangle \), then the field has no rotational movement about any point in the region and is termed **conservative**. This indicates that the vector field can be described by a scalar potential function.
Potential Function
In vector calculus, a **potential function** is a scalar function whose gradient yields a given vector field. So, when a vector field is conservative, it can be expressed as the gradient of a potential function.For a given vector field \( \mathbf{F} = \langle F_1, F_2, F_3 \rangle \), the potential function \( \phi(x, y, z) \) satisfies:
  • \( \frac{\partial \phi}{\partial x} = F_1 \)
  • \( \frac{\partial \phi}{\partial y} = F_2 \)
  • \( \frac{\partial \phi}{\partial z} = F_3 \)
To find this, integrate each component with respect to its variable, up to a constant function of the other variables. For example, integrating \( \frac{\partial \phi}{\partial x} = yz \) with respect to \( x \) gives \( \phi(x, y, z) = xyz + g(y, z) \). Continue similarly for each of the other variables.In our solved exercise, these integrations all reveal a similar structure, leading to the **potential function** \( \phi(x, y, z) = xyz \). This function encapsulates the conservative nature of our vector field, allowing us to explore further calculations.
Partial Derivatives
**Partial derivatives** are crucial in multivariable calculus. They provide an understanding of how a function changes as one specific variable changes, holding others constant.When dealing with vector fields and potential functions, partial derivatives are used to connect the field components to the potential function. For the field \( \mathbf{F} = \langle yz, xz, xy \rangle \):
  • The partial derivative \( \frac{\partial F_1}{\partial x} \) gives information about how \( F_1 = yz \) changes with \( x \).
  • Similarly, \( \frac{\partial F_2}{\partial y} \) shows how \( F_2 = xz \) changes with \( y \), and so on.
In finding a potential function, partial derivatives allow you to write equations like \( \frac{\partial \phi}{\partial x} = yz \). Solving these involves integrating with respect to single variables, providing insight into the structure and behavior of potential functions. By mastering partial derivatives, you'll have a powerful toolset to tackle problems in multidimensional calculus and physics.

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Most popular questions from this chapter

A square plate \(R=\\{(x, y): 0 \leq x \leq 1,\) \(0 \leq y \leq 1\\}\) has a temperature distribution \(T(x, y)=100-50 x-25 y\) a. Sketch two level curves of the temperature in the plate. b. Find the gradient of the temperature \(\nabla T(x, y)\) c. Assume that the flow of heat is given by the vector field \(\mathbf{F}=-\nabla T(x, y) .\) Compute \(\mathbf{F}\) d. Find the outward heat flux across the boundary \(\\{(x, y): x=1,0 \leq y \leq 1\\}\) e. Find the outward heat flux across the boundary \(\\{(x, y): 0 \leq x \leq 1, y=1\\}\)

The French physicist André-Marie Ampère \((1775-1836)\) discovered that an electrical current \(I\) in a wire produces a magnetic field \(\mathbf{B} .\) A special case of Ampère's Law relates the current to the magnetic field through the equation \(\oint_{C} \mathbf{B} \cdot d \mathbf{r}=\mu I,\) where \(C\) is any closed curve through which the wire passes and \(\mu\) is a physical constant. Assume that the current \(I\) is given in terms of the current density \(\mathbf{J}\) as \(I=\iint_{S} \mathbf{J} \cdot \mathbf{n} d S\) where \(S\) is an oriented surface with \(C\) as a boundary. Use Stokes' Theorem to show that an equivalent form of Ampère's Law is \(\nabla \times \mathbf{B}=\mu \mathbf{J}\)

Find the exact points on the circle \(x^{2}+y^{2}=2\) at which the field \(\mathbf{F}=\langle f, g\rangle=\left\langle x^{2}, y\right\rangle\) switches from pointing inward to outward on the circle, or vice versa.

a. For what values of \(a, b, c,\) and \(d\) is the field \(\mathbf{F}=\langle a x+b y, c x+d y\rangle\) conservative? b. For what values of \(a, b,\) and \(c\) is the field \(\mathbf{F}=\left\langle a x^{2}-b y^{2}, c x y\right\rangle\) conservative?

Find a vector field \(\mathbf{F}\) with the given curl. In each case, is the vector field you found unique? $$\operatorname{curl} \mathbf{F}=\langle 0, z,-y\rangle$$

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