{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

# Lecture 3 - Why Why Are we spending so much time on these...

This preview shows pages 1–5. Sign up to view the full content.

Why? Are we spending so much time on these abstract things called electric fields? Because E-fields are real. They cause charges to move, currents to flow, and your toaster and brain cells to work. And because the basic rules for electromagnetism are rules about electric fields and magnetic fields. Why so much calculus in studio and no calculus on HW? Because the basic rules for electromagnetism can only be expressed in terms of calculus. And despite the good job are math department has done, applying calculus to physics problems the first time benefits from being in a room where you can get a lot of help. There will be 1 or 2 “calculus” problems on quiz 1!

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

View Full Document
Electrical effects of dust The van de Graaf generator attracts small neutral The van de Graaf generator attracts small neutral objects (dust, pollen, water droplets) to it when charged. What would happen to one of these objects if it touched the generator. A. Nothing much; it would bounce off at the same speed it contacted the generator contacted the generator. B. It would stick to the generator. C. It would be repelled from the generator at high speed.
The principle of superposition The electric field at any point in space r is the sum of the electric fi ld h ld b d d b ll h l i h i h fields at r that would be produced by all the electric charges in the universe. = N i r r 1 1 r r Thi i t ll d h f E fi ld l l ti I = × × × = i i i i i i r r r r Q r r E 1 2 0 | | | | 4 ) , ( r r r r r r r πε This is actually good enough for any E-field calculation. In many situations however, there are so many charges that are spread out so smoothly that we can think of the charge in coming in a continuous charge density. This density can come in the form of a charge per unit length, usually called λ ; a charge per unit area, called σ , or a charge per unit volume, called ρ .

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

View Full Document
Effective point charge
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