Chapter 9: Vector Calculus
Section 9.7: Conservative and Solenoidal Fields
Example 9.7.8
Find a scalar potential for F=2⁢x⁢z+y2 i+2 x y−z3 j+x2−3⁢y⁢z2 k.
Solution
Mathematical Solution
To implement Recipe 1, Table 9.7.4, form and evaluate the following integrals.
∫axb2+2⁢c⁢t dt+∫by−c3+2⁢t⁢x dt+∫cz−3⁢t2⁢y+x2 dt = b⁢c3−y⁢z3−a2⁢c−a⁢b2+x2⁢z+x⁢y2
The constants a,b, and c can be taken as zero, so the simplest scalar potential for F is then
−y⁢z3+x2⁢z+x⁢y2
Maple Solution - Interactive
Table 9.7.8(a) provides a solution via the ScalarPotential command accessed through the Context Panel.
Initialize
Tools≻Load Package: Student Vector Calculus
Loading Student:-VectorCalculus
Tools≻Tasks≻Browse: Calculus - Vector≻ Vector Algebra and Settings≻ Display Format for Vectors
Press the Access Settings button and select "Display as Column Vector"
Display Format for Vectors
Define the vector field F
Enter the components of F in a free vector. Context Panel: Evaluate and Display Inline
Context Panel: Student Vector Calculus≻Conversions≻To Vector Field
Context Panel: Assign to a Name≻F
2 x z+y2,2 x y−z3,x2−3 y z2 = →to Vector Field →assign to a nameF
Obtain a scalar potential for F
Write the name F. Context Panel: Evaluate and Display Inline
Context Panel: Student Vector Calculus≻Scalar Potential
F = →scalar potential−y⁢z3+x2⁢z+x⁢y2
Table 9.7.8(a) Solution by the ScalarPotential command accessed through the Context Panel
Table 9.7.8(b) implements Recipe 1, Table 9.7.4, and verifies that the result is consistent with the scalar potential found by Maple's ScalarPotential command.
Define the components of F as the functions fx,y,z, gx,y,z, and hx,y,z
Context Panel: Assign Function
fx,y,z=F1→assign as functionf
gx,y,z=F2→assign as functiong
hx,y,z=F3→assign as functionh
Implement Recipe 1, Table 9.7.4
Calculus palette: Definite-integral operator Press the Enter key.
Context Panel: Simplify≻Simplify
Context Panel: Evaluate at a Point≻a=b=0 (See the figure to the right.)
∫axft,b,c ⅆt+∫bygx,t,c ⅆt+∫czhx,y,t ⅆt
b2⁢x−a+c⁢−a2+x2−c3⁢y−b+x⁢−b2+y2−y⁢−c3+z3+x2⁢z−c
= simplify
b⁢c3−y⁢z3−a2⁢c−a⁢b2+x2⁢z+x⁢y2
→evaluate at point
Table 9.7.8(b) Implementation of Recipe 1, Table 9.7.4
Maple Solution - Coded
Install the Student VectorCalculus package.
withStudent:-VectorCalculus:
Set display of vectors via BasisFormat.
BasisFormatfalse:
Define F via the VectorField command.
F≔VectorField2 x z+y2,2 x y−z3,x2−3 y z2:
Use the ScalarPotential command to obtain a scalar potential for F
ScalarPotentialF = −y⁢z3+x2⁢z+x⁢y2
Table 9.7.8(c) Application of the ScalarPotential command
Table 9.7.8(d) applies Recipe 1, Table 9.7.4, to obtain the requisite scalar potential.
Use the unapply command to define the components of F as the functions fx,y,z, gx,y,z, and hx,y,z
f≔unapplyF1,x,y,z:
g≔unapplyF2,x,y,z:
h≔unapplyF3,x,y,z:
Use the Int command to write the integrals of Recipe 1, Table 9.7.4
Intft,b,c,t=a..x+Intgx,t,c,t=b..y+Inthx,y,t,t=c..z
∫axb2+2⁢c⁢tⅆt+∫by−c3+2⁢t⁢xⅆt+∫cz−3⁢t2⁢y+x2ⅆt
Access the top-level int command by prefixing "colon-dash" to int
u≔:-intft,b,c,t=a..x+:-intgx,t,c,t=b..y+:-inthx,y,t,t=c..z
Apply the simplify and eval commands to set a=b=c=0.
simplifyevalu,a=0,b=0,c=0
Table 9.7.8(d) Implementation of Recipe 1, Table 9.7.4
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