Chapter 13: Problem 4
Find \((\) a) the curl and (b) the divergence of the vector field. $$\mathbf{F}(x, y, z)=\sin y z \mathbf{i}+\sin z x \mathbf{j}+\sin x y \mathbf{k}$$
Short Answer
Expert verified
Curl: \((x \cos xy - x \cos zx)\mathbf{i} + (y \cos yz - y \cos xy)\mathbf{j} + (z \cos zx - z \cos yz)\mathbf{k}\), Divergence: 0.
Step by step solution
01
Identify Components of the Vector Field
The given vector field is defined as \( \mathbf{F}(x, y, z) = \sin yz \mathbf{i} + \sin zx \mathbf{j} + \sin xy \mathbf{k} \). Identify the components: \( F_1 = \sin yz \), \( F_2 = \sin zx \), and \( F_3 = \sin xy \).
02
Calculate the Curl of the Vector Field
The curl of a vector field \( \mathbf{F} = (F_1, F_2, F_3) \) is given by: \[ abla \times \mathbf{F} = \left( \frac{\partial F_3}{\partial y} - \frac{\partial F_2}{\partial z} \right) \mathbf{i} + \left( \frac{\partial F_1}{\partial z} - \frac{\partial F_3}{\partial x} \right) \mathbf{j} + \left( \frac{\partial F_2}{\partial x} - \frac{\partial F_1}{\partial y} \right) \mathbf{k} \] Calculate each component:- \( \mathbf{i} \) component: \( \frac{\partial F_3}{\partial y} = x \cos xy \), \( \frac{\partial F_2}{\partial z} = x \cos zx \) Result: \( x \cos xy - x \cos zx \)- \( \mathbf{j} \) component: \( \frac{\partial F_1}{\partial z} = y \cos yz \), \( \frac{\partial F_3}{\partial x} = y \cos xy \) Result: \( y \cos yz - y \cos xy \)- \( \mathbf{k} \) component: \( \frac{\partial F_2}{\partial x} = z \cos zx \), \( \frac{\partial F_1}{\partial y} = z \cos yz \) Result: \( z \cos zx - z \cos yz \)The curl is: \[ abla \times \mathbf{F} = (x \cos xy - x \cos zx) \mathbf{i} + (y \cos yz - y \cos xy) \mathbf{j} + (z \cos zx - z \cos yz) \mathbf{k} \]
03
Calculate the Divergence of the Vector Field
The divergence of a vector field \( \mathbf{F} = (F_1, F_2, F_3) \) is given by: \[ abla \cdot \mathbf{F} = \frac{\partial F_1}{\partial x} + \frac{\partial F_2}{\partial y} + \frac{\partial F_3}{\partial z} \] Calculate each term:- \( \frac{\partial F_1}{\partial x} = 0 \), since \( \sin yz \) does not depend on \( x \).- \( \frac{\partial F_2}{\partial y} = 0 \), since \( \sin zx \) does not depend on \( y \).- \( \frac{\partial F_3}{\partial z} = 0 \), since \( \sin xy \) does not depend on \( z \).Thus, the divergence is:\[ abla \cdot \mathbf{F} = 0 + 0 + 0 = 0 \]
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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
Vector calculus involves understanding various operations on vector fields, one of which is the curl. The curl of a vector field measures the rotation at a point within the field. Its practical use is in fluid dynamics and electromagnetism to determine the tendency of a fluid or field to rotate at a given point. For a vector field \( \mathbf{F} = (F_1, F_2, F_3) \), the curl is a new vector field defined by the following cross product formula:\[ abla \times \mathbf{F} = \left( \frac{\partial F_3}{\partial y} - \frac{\partial F_2}{\partial z} \right) \mathbf{i} + \left( \frac{\partial F_1}{\partial z} - \frac{\partial F_3}{\partial x} \right) \mathbf{j} + \left( \frac{\partial F_2}{\partial x} - \frac{\partial F_1}{\partial y} \right) \mathbf{k} \]Let's examine this further:
- \( \mathbf{i} \) component: It involves the partial derivatives \( \frac{\partial F_3}{\partial y} \) and \( \frac{\partial F_2}{\partial z} \).
- \( \mathbf{j} \) component: This one involves \( \frac{\partial F_1}{\partial z} \) and \( \frac{\partial F_3}{\partial x} \).
- \( \mathbf{k} \) component: Here, you calculate \( \frac{\partial F_2}{\partial x} \) and \( \frac{\partial F_1}{\partial y} \).
Divergence of a Vector Field
The divergence is another key concept in vector calculus. Divergence determines how much a vector field spreads out or converges at a point. In essence, it measures the 'outflow' of a field at any given point and is used in fields such as physics to explain concepts related to fluid flow, electromagnetism, and more. For a vector field \( \mathbf{F} = (F_1, F_2, F_3) \), the divergence is a scalar given by:\[ abla \cdot \mathbf{F} = \frac{\partial F_1}{\partial x} + \frac{\partial F_2}{\partial y} + \frac{\partial F_3}{\partial z} \]In the context of the given exercise:
- The first component \( F_1 = \sin yz \) does not change with \( x \), resulting in a partial derivative of zero.
- The second component \( F_2 = \sin zx \) is independent of \( y \), so its partial derivative also results in zero.
- Lastly, \( F_3 = \sin xy \) does not vary with \( z \), leading to another zero.
Vector Field Analysis
Vector field analysis can be quite intuitive once you understand the tools and operations involved. A vector field associates every point in space with a vector, often representing quantities like velocity, force, or other directional data across a spatial domain. Analysing vector fields often involves examining both the curl and divergence as discussed above:
- Curl helps to understand the rotational nature, like vortices or swirling motions.
- Divergence assists in examining the spread or convergence, like sources or sinks within the field.
- Fluid Dynamics: Understanding how fluid elements move and rotate.
- Electromagnetism: Calculating and predicting fields generated by electric charges.