Thank you for taking the time to review my work. I am posting problems with solutions, but I'm not sure if my solutions are correct. The problems are exactly how I have them written in front of me. These are mostly conceptual questions, which require a short answer of some sort.(adsbygoogle = window.adsbygoogle || []).push({});

Q1. A chargeQcoulombsis placed at the origin of co-ordinates. Give the threevectorforce componentson a charge -Qat a point P(x,y,z).

My Answer: Fx = (k|Q||-Q|)/(r^2); Fy = (k|Q||-Q|)/(r^2); Fz = (k|Q||-Q|)/(r^2). The three vector forced components on charge -Q (at point P) would be on each of the three different axes: x,y, and z. After some calculations, you can use all three to find the direction and magnitude of charge -Q at point P.

Q2. A chargeqis placed fixed at the origin. A thin hollow metal sphere radiusais centered at the origin and a charge ofqis placed initially on the outside surface. After the charge has rearranged itself give the electric field

(i) at a point P(x,y,z) inside the sphere, r<a;

(ii) in the medal of the sphere, r=a;

(iii) outside the sphere, r>a.

(iv) What is the charge on the inner metal surface?

My answer:

(i) The electric field must be zero because it is that equilibrium inside the sphere. E=0

(ii) the electric field in the metal of the sphere is equal to charge q at the origin.

(iii) Outside this year, the electric field is E=(q)/(4)(pi)(Eo)(r^2). the electric field outside is uniformly spread along the surface. [got equations from book, not sure if correct].

(iv) the charge on the inner metal surface would be opposite or negative to the charge q.

Q4. Give the potential as a function of r for the three regions in problem Q2. Hint: use the fact that electric fields and potentials from different charges add. And the standard results that a sphere of radiusacentered at the origin and uniformly charged withqhas potentialkq/aifr<aandkq/rifr>a.

My answer:

Using the hint, this is what I came up with...It's not much, but I hoping someone could help me out some more.

From Q2, using the info from the problem itself:

(i) kq/a

(ii) a=r so then kq/a = kq/r

(iii) kq/r

the different charges add, so i tried to add them

kq/a + r + kq/r

get them all the same denominator

kqr/ar + ar^2/ar + kqa/ar

so then i came up with the equation which leads me no where really

(kqr + ar^2 + kqa)/(ar) <-----this would then equal the potential as a function of r....somehow

Hopefully you have better luck with any of these problems than I did. Any input on any question would be great. Thanks for you time.

alexman

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# Homework Help: Physics Questions - Electric Fields, Electric Potential, etc

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