PHY 2049: Physics II There is a proposal to move the final to Monday (8/4) from Wednesday (8/6). Any objections? To purchase Wiley Plus, the URL is: .

PHY 2049: Physics II

There is a proposal to move the final to Monday (8/4) from Wednesday (8/6). Any objections?

To purchase Wiley Plus, the URL is:

http://he-cda.wiley.com/WileyCDA/Section/id-320351.html

PHY 2049: Physics II

About bicycle riding: If some one shows you a trick, it means that, It is possible to do that trick The person who showed you, can do the

trick It does not mean that you can do the trick.

Try it a lot of times and you can too.

PHY 2049: Physics II

Coulomb’s law: Two kinds of charges,

positive and negative, unlike attract, like repel.

Electrons and Protons:q = ± 1.602 x 10-19 C Current I = dq/dt

1 Amp. = 1 C/s Add forces as vectors

rr

qqkF ˆ

212

21

PHY 2049: Physics II

A ruleTry to calculate the force magnitude by ignoring the signs of charges. Then assign the direction by looking at the signs.

Never do both (using the charge signs in the calculation of the force and then assign the direction).

PHY 2049: Physics II

Charges are introduced by rubbing

(depends) Touching (same) By induction

(opposite)

PHY 2049: Physics II

Balls are touched and then separated. Rank them by Charge left Magnitude of Force before After Charge transferred 3,1,2

PHY 2049: Physics II

Force on the center charge = 6kq2/d2

d

PHY 2049: Physics II q1 = q4 = Q; q2 = q3 =

q what is Q/q so that the

force on 1 is zero All charges same sign.

There is no solution. Q and q different sign.

There is a possible solution.

Is the answer the same if the force on 3 is to be zero

PHY 2049: Physics II

What is the force on the central chlorine ion?

Suppose that we put in an electron that sits on a cesium site and neutralizes it, which way does the Chlorine move?

PHY 2049: Physics II

Electric Field Force F = qE

E = k ∑ rˆ qi/ri2

enviro

nment

Test charge

•Electric field lines denote direction

•Their density represents magnitude

•They do not cross

PHY 2049: Physics II q1 = 2Q q2 = - 2Q q3 = -4Q

E at origin

PHY 2049: Physics II

z

Rz

qzkE ˆ

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