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I'm working on my first assignment in an EM class and I have a couple questions (this might be a long post). Understand I'm a part time student and I live an hour away from the university and work 40+ hours a week... time is limited. I have a 5 problem assignment and a million questions.

1. For a given charge system, the flux density D= r^2sin(theta)ahat_r+sin(theta)cos(phi)ahat_phi C/m^2. Determine

a)the Charge density at point (1m,45 deg, 90 deg)

b)Find the force on a point charge of 1nC located @ (1m,1m,2m)

a) Plug the point into the flux density?

b) convert spherical to cartesian coordinates find R(trig) and coulombs law for charges in free space 9x10^9(Q_1Q_2/R^2)

a)so from my understanding a charge density requires a surface area, I am supplied with a point so I thought I'd just put the point in the equation and evaluate from 0 to 1 0 to 45 and 0 to 90... everything cancels but root2/2 which I believe is my answer but I have a point not a surface area.

b)I find R to be root6 using the given charge and the found charge from the previous part put into coulombs law yields 3root2/4 N

The next question is a potential quesiton and I'm lost

The potential field with Epsilon_r = 10 is V=12x^2y find E, P, and D

I don't know where to begin,

3) a square conductive loop 10cm/side is centered at origin carries 10mA current clockwise viewed from the +z direction find the magnetic field intensity at point (0,0,10)

I have sketched it out and found the distance from the point to the corner to be root110 and the shortest point to the line to be 5root2, all the evaluations I can find that come close to this problem all use circles around the point not squares... I'm lost

it sound's like and Ampere's Law problem

intH dot dl = I enclosed

4) Given the magnetice field H=3y^2ahat_y A/m find the current passing through a square in the xy-plane that has one corner at origin and the opposite corner at (2,2,0)

sounds like the opposite of the last problem still stuck

5) in a given region of space, the magnetic vector potential is given by A=5cos(pi y)xhat+(2+sinpix)zhat (Wb/m) determine B and flux passing through a square loop with 0.25 m long centered at the origin of the xy plane and its edges are parallel to the x and y axis.

???

I haven't dug into the lecture notes and book for this one yet this is due next monday... like I said it's my first assignment and we haven't worked any practice problems in class. I want to understand the correlations between current and magnetic field... that would help with 3&4. Any direction on this assignment would be greatly appreciated.

Thank you

David

**1. Homework Statement**1. For a given charge system, the flux density D= r^2sin(theta)ahat_r+sin(theta)cos(phi)ahat_phi C/m^2. Determine

a)the Charge density at point (1m,45 deg, 90 deg)

b)Find the force on a point charge of 1nC located @ (1m,1m,2m)

**2. Homework Equations**a) Plug the point into the flux density?

b) convert spherical to cartesian coordinates find R(trig) and coulombs law for charges in free space 9x10^9(Q_1Q_2/R^2)

**3. The Attempt at a Solution**a)so from my understanding a charge density requires a surface area, I am supplied with a point so I thought I'd just put the point in the equation and evaluate from 0 to 1 0 to 45 and 0 to 90... everything cancels but root2/2 which I believe is my answer but I have a point not a surface area.

b)I find R to be root6 using the given charge and the found charge from the previous part put into coulombs law yields 3root2/4 N

The next question is a potential quesiton and I'm lost

The potential field with Epsilon_r = 10 is V=12x^2y find E, P, and D

I don't know where to begin,

3) a square conductive loop 10cm/side is centered at origin carries 10mA current clockwise viewed from the +z direction find the magnetic field intensity at point (0,0,10)

I have sketched it out and found the distance from the point to the corner to be root110 and the shortest point to the line to be 5root2, all the evaluations I can find that come close to this problem all use circles around the point not squares... I'm lost

it sound's like and Ampere's Law problem

intH dot dl = I enclosed

4) Given the magnetice field H=3y^2ahat_y A/m find the current passing through a square in the xy-plane that has one corner at origin and the opposite corner at (2,2,0)

sounds like the opposite of the last problem still stuck

5) in a given region of space, the magnetic vector potential is given by A=5cos(pi y)xhat+(2+sinpix)zhat (Wb/m) determine B and flux passing through a square loop with 0.25 m long centered at the origin of the xy plane and its edges are parallel to the x and y axis.

???

I haven't dug into the lecture notes and book for this one yet this is due next monday... like I said it's my first assignment and we haven't worked any practice problems in class. I want to understand the correlations between current and magnetic field... that would help with 3&4. Any direction on this assignment would be greatly appreciated.

Thank you

David

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