# Answer to Sample Tests 1 - Dr Gangopadhyaya Sample Tests I...

This preview shows pages 1–2. Sign up to view the full content.

Dr. Gangopadhyaya Sample Tests I Physics 351 February 19, 2006 Questions from one of you First question: On of the sample tests (TST1 351 F01.pdf), you asked to determine the divergence of the electric field in the form ( q/ 4 * Pi * epsilon ) * ( r - a ) /abs ( r - a ) 3 , where r and a are vectors and a = ( a, 0 , 0). To answer the question, can we just invoke gauss’ law and say that ∇ · E = ( q/epsilon ) δ ( r - a )? I am not sure how we would derive that besides stating the answer? If it does require derivation, I am not sure how to go about doing it because the charge is not at the origin. Any advice would be greatly helpful. Thanks for your time. Second question: In sample test TST1 351 S2005.pdf, problem #4 defines the vector field = (1/r)*unit vector phi, and its asks to determine curl and integrate over a disk of radius R on the xy plane. When I use the formula for curl in cylindrical coordinates, and even when i use maple, i get curl = (1 /r 2 ) * (cos( θ ) / sin( θ )) * ˆ r . The very first thing i notice is that the curl is in r hat direction, and da for the disk should be in theta direction (da = dr*r*sin(theta)*dphi*unit vector theta), right? This

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### What students are saying

• As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

Kiran Temple University Fox School of Business ‘17, Course Hero Intern

• I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

Dana University of Pennsylvania ‘17, Course Hero Intern

• The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

Jill Tulane University ‘16, Course Hero Intern