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Chapter One: Vector Analysis The use of vectors and vector analysis ...

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Electromagnetic <strong>The</strong>orem<br />

(Dr. Omed Ghareb Abdullah) University <strong>of</strong> Sulaimani –College <strong>of</strong> Science – Physics Department<br />

Example(2):<br />

(a). find the length <strong>of</strong> each <strong>of</strong> the curves: 3,<br />

<br />

,<br />

4 2<br />

z cons tan t.<br />

<br />

(b). Calculate the area <strong>of</strong> the surfaces area defined by: z 1, 1 3 , 0 <br />

4<br />

(c). determine the volume <strong>of</strong> the region defined by: 1 r 3 ,<br />

2<br />

<br />

, <br />

2 3 6 2<br />

Solution:<br />

(a).<br />

dl d<br />

<br />

<br />

dl <br />

/ 2<br />

<br />

d<br />

3 ( / 2 <br />

/ 4)<br />

<br />

4<br />

/ 4<br />

3<br />

l unit<br />

length<br />

(b)<br />

ds d<br />

d<br />

<br />

3 / 4<br />

1 4<br />

3 /<br />

2<br />

<br />

ds <br />

d<br />

d<br />

( ) ( )<br />

4 <br />

2<br />

1 0<br />

4<br />

1<br />

0<br />

<br />

S <br />

unit<br />

<strong>of</strong><br />

area<br />

(c).<br />

dv r<br />

2<br />

sin<br />

dr d<br />

d<br />

<br />

<br />

dv <br />

3 2<br />

/ 3 / 2<br />

<br />

1 / 2<br />

/ 6<br />

3<br />

r<br />

sin<br />

dr d<br />

d<br />

<br />

3<br />

1<br />

v (27 1)<br />

(cos<br />

/ 2 cos 2<br />

/ 3) ( / 2 / 6)<br />

3<br />

1<br />

<br />

13<br />

v (26) (0<br />

0.5) (<br />

) v unit <strong>of</strong><br />

3<br />

3<br />

9<br />

r<br />

2<br />

volume<br />

3<br />

1<br />

( cos<br />

)<br />

2<br />

/ 3<br />

/ 2<br />

( )<br />

/ 2<br />

/ 6<br />

Example(3):<br />

Find the gradient <strong>of</strong> the following scalar functions:<br />

a. U 4 x z<br />

2 3 y z , b. 2 ( z 2 2<br />

W 1)<br />

cos<br />

, c. V r cos cos<br />

.<br />

(a). <br />

U (<br />

<br />

x<br />

aˆ<br />

x<br />

<br />

<br />

y<br />

aˆ<br />

y<br />

<br />

<br />

z<br />

aˆ<br />

)(4xz<br />

z<br />

2<br />

3yz)<br />

<br />

4 z<br />

2<br />

aˆ<br />

x<br />

3z aˆ<br />

y<br />

(8xz<br />

3y)<br />

aˆ<br />

z<br />

(b).<br />

<br />

<br />

W ( aˆ<br />

<br />

<br />

1 <br />

aˆ<br />

<br />

<br />

<br />

<br />

z<br />

aˆ<br />

)(2 (<br />

z<br />

1) cos)<br />

2( z<br />

1) cos<br />

aˆ<br />

2 ( z<br />

1) sin<br />

aˆ<br />

4 z cos<br />

ˆ<br />

2<br />

2<br />

2<br />

z <br />

<br />

a z<br />

56

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