/*! 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 31 Gradient fields Find the gradien... [FREE SOLUTION] | 91Ó°ÊÓ

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Gradient fields Find the gradient field \(\mathbf{F}=\nabla \varphi\) for the following potential functions \(\varphi.\) $$\varphi(x, y)=x / y$$

Short Answer

Expert verified
Answer: The gradient field is \(\mathbf{F}=\left\langle \frac{1}{y}, -\frac{x}{y^2} \right\rangle\).

Step by step solution

01

Compute the partial derivatives

Calculate the partial derivatives of \(\varphi(x,y) = x/y\) with respect to \(x\) and \(y\) separately: $$ \frac{\partial \varphi}{\partial x} = \frac{\partial}{\partial x} \frac{x}{y}, \quad \frac{\partial \varphi}{\partial y} = \frac{\partial}{\partial y} \frac{x}{y} $$
02

Find \(\frac{\partial \varphi}{\partial x}\)

When differentiating with respect to \(x\), \(y\) is treated as a constant: $$ \frac{\partial \varphi}{\partial x} = \frac{\partial}{\partial x} \frac{x}{y} = \frac{1}{y} $$
03

Find \(\frac{\partial \varphi}{\partial y}\)

When differentiating with respect to \(y\), \(x\) is treated as a constant: $$ \frac{\partial \varphi}{\partial y} = \frac{\partial}{\partial y} \frac{x}{y} = -\frac{x}{y^2} $$
04

Write the gradient field \(\mathbf{F}\)

Combine the partial derivatives into the gradient vector: $$ \mathbf{F} = \nabla \varphi = \left\langle \frac{\partial \varphi}{\partial x}, \frac{\partial \varphi}{\partial y}\right\rangle = \left\langle \frac{1}{y}, -\frac{x}{y^2} \right\rangle $$ The gradient field is \(\mathbf{F}=\left\langle \frac{1}{y}, -\frac{x}{y^2} \right\rangle\).

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Key Concepts

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

Potential Functions
In the realm of multivariable calculus, potential functions play a crucial role in understanding the behavior of vector fields. A potential function, often denoted as \( \varphi \), is a scalar function whose gradient produces a given vector field. This relationship is symbolized as \( \mathbf{F} = abla \varphi \), where \( abla \), known as the nabla operator, represents the gradient. The gradient field resulting from the potential function can be thought of as describing the direction and rate of the steepest ascent at any point in the space.

For the exercise given, the potential function is \( \varphi(x, y) = x/y \). This function implies that there exists a gradient field associated with it, which we can calculate by finding the partial derivatives with respect to both variables. Potential functions provide deep insights into physical phenomena such as electromagnetic fields or gravitational forces, where the potential function represents the potential energy per unit charge or mass, respectively. Recognizing and working with potential functions allow us to solve many physical and geometrical problems using calculus.
Partial Derivatives
The concept of partial derivatives is integral to multivariable calculus. Essentially, a partial derivative represents the rate of change of a multivariable function when one variable is allowed to vary while the others are held constant. Symbolically, the partial derivative of a function \( f \) with respect to the variable \( x \) is denoted as \( \frac{\partial f}{\partial x} \).

In the given exercise, computing the partial derivatives of \( \varphi(x,y) = x/y \) is the first step toward finding the gradient field. The exercise demonstrates this by differentiating \( \varphi \) with respect to \( x \) and \( y \) separately, treating the other variable as a constant during each process. This characteristic is the foundational difference between partial and ordinary derivatives, where the latter involves a function of a single variable. Understanding how to compute partial derivatives is essential for students tackling problems involving functions of several variables and is widely applied in diverse fields like economics, physics, and engineering.
Calculus
Calculus is a branch of mathematics centered around the study of change and motion. It's split into two major areas: differential calculus, which deals with rates of change and slopes of curves, and integral calculus, concerning the accumulation of quantities and the areas under and between curves.

The exercise provided is a practical application of differential calculus—more specifically, multivariable calculus. The use of calculus in this context allows us to calculate gradients, which convey the direction and magnitude of the steepest ascent of a function. It's through these gradients that we understand how a physical quantity changes with respect to multiple variables in space. In the world around us, calculus aids in modeling dynamics ranging from the motion of celestial bodies to the behavior of subatomic particles. For students, it's a powerful tool that unveils the intricacies of complex systems by breaking them down into fundamental principles that can be analyzed and understood.

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Most popular questions from this chapter

Prove that if \(\mathbf{F}\) satisfies the conditions of Stokes' Theorem, then \(\iint_{S}(\nabla \times \mathbf{F}) \cdot \mathbf{n} d S=0\) where \(S\) is a smooth surface that encloses a region.

The cone \(z^{2}=x^{2}+y^{2},\) for \(z \geq 0,\) cuts the sphere \(x^{2}+y^{2}+z^{2}=16\) along a curve \(C\) a. Find the surface area of the sphere below \(C,\) for \(z \geq 0\). b. Find the surface area of the sphere above \(C\). c. Find the surface area of the cone below \(C,\) for \(z \geq 0\).

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 \(\\{(x, y): 0 \leq x \leq 1, y=1\\}\)

Begin with the paraboloid \(z=x^{2}+y^{2},\) for \(0 \leq z \leq 4,\) and slice it with the plane \(y=0\) Let \(S\) be the surface that remains for \(y \geq 0\) (including the planar surface in the \(x z\) -plane) (see figure). Let \(C\) be the semicircle and line segment that bound the cap of \(S\) in the plane \(z=4\) with counterclockwise orientation. Let \(\mathbf{F}=\langle 2 z+y, 2 x+z, 2 y+x\rangle\) a. Describe the direction of the vectors normal to the surface that are consistent with the orientation of \(C\). b. Evaluate \(\iint_{S}(\nabla \times \mathbf{F}) \cdot \mathbf{n} d S\) c. Evaluate \(\oint_{C} \mathbf{F} \cdot d \mathbf{r}\) and check for agreement with part (b).

\(A\) scalar-valued function \(\varphi\) is harmonic on a region \(D\) if \(\nabla^{2} \varphi=\nabla \cdot \nabla \varphi=0\) at all points of \(D\) Show that the potential function \(\varphi(x, y, z)=|\mathbf{r}|^{-p}\) is harmonic provided \(p=0\) or \(p=1,\) where \(\mathbf{r}=\langle x, y, z\rangle .\) To what vector fields do these potentials correspond?

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