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  1. M

    Wires Magnetic field question

    Two long straight wires piece on the plane of the paper at vertices of an equilateral triangle. They each carry 2 A, out of the paper. The magnetic field at the third vertex has a magnetic of...? The third vertex is the top of the equilateral triangle. I don't know what equation to use to...
  2. M

    Easy one

    I thought because the fish was placed in the center of the sphere, the distance of the object would be the distance of the radius. I don't, however, know the distance of the observer. Is there a way to explain where the observer would see the fish and the pattern without that distance? How...
  3. M

    Easy one

    i just need a little help with a relatively easy lens question A small fish is cast into the center of a glass sphere of radius R=5 cm and n=1.5. Where will an observer see the fish? Where will the observer see a decorative pattern painted on the back side of a sphere? So, I thought I...
  4. M

    Energy stored in an inductor

    thank you! thanks so much!
  5. M

    Energy stored in an inductor

    help please!!! I need a little help here. The question says to consider an inductor with L=16H and an internal resistance of 0.10 ohms. We wish to use this inductor to store 0.10 MJ of energy. What is the rate at which energy is lost to Joule heating in this system? It is not practical to...
  6. M

    Directional Derivative Problem

    Thanks! Thank you so much!! First of all, I did copy the problem wrong...the last part of the equation was (1-t^3)k. So, it works out! I don't know why I thought that just taking the derivative of r(t) and then using that would work! Thanks again!
  7. M

    Directional Derivative Problem

    Hello! I have a question about a problem I am trying to work out. The question asks to find the directional derivative of f(x,y,z)=x^2+yz at the point (1,-3,2) in the direction of the path r(t)=t^2i + 3tj+(1-t^2)k. Ok, first do I find the derivative of r(t) to get 3j +t(2i-2k) and then use...
  8. M

    Larmor frequency

    Can someone please explain Larmor frequency to me? (like how the equation w=q*B/2m is derived?) I would greatly appreciate it!!
  9. M

    Calc 3 directional derivative question

    The question asks: Find the directional derivative of f (x, y, z) = z ln (x/y) at (1, 1, 2) toward the point (2, 2, 1). What I did was find the distance between the two points to be the directional vector (i+j-k) and then I took the norm of the direction vector. so my unit vector =...
  10. M

    Light bulbs in parallel and series

    Q: You have a light bulb in series with a battery to make a complete circuit. Then you have another circuit with two light bulbs in parallel connected to a battery. The lightbulbs in all the circuits are identical and the batteries are the same in the two circuits. Before working with these...
  11. M

    Capacitors in Parallel and Series

    oops! The circuit from point a goes to a capacitor of 3uF, then leads to 2 capacitors in series (2uF and 5uF) that are together parallel to a capacitor of 1uF. From the parallel circuit section you get to point b. Does that make sense? I tried to draw it out...but I guess it didn't work:) Thanks!
  12. M

    Capacitors in Parallel and Series

    Hello. I have a brain fart and this combination circuit has me stumped. Here is a crude representation of the circuit. I had no problem finding the total capacitance (1.34uF), but the second part asks you to find the charge on each of the capacitors, assuming that the potential difference...
  13. M

    Easy calc 3 question: points on a plane

    The question asks: Which of the points P(3,2,1), Q(2,3,1),R(1,4,1) lie on the plane 3(x-1)+4y-5(z+2)=0? I know this is a pretty easy problem...but I am drawing a blank on where to start? Should I form vectors from each point ? If so, then what? A little lost! Thanks
  14. M

    What is the total energy of the point charge?

    I need help with this question. I can't see the motion. I have Consider a solid sphere of radius R with a charge Q distributed uniformly. Suppose that a point charge 'q' of mass 'm', with a sign opposite that of Q, is free to move within the solid sphere. Charge q is placed at rest on the...
  15. M

    One more calc 3 problem

    you're awesome Thanks again. You are awesome.
  16. M

    One more calc 3 problem

    The question asks to find each sphere that passes through the point (5,1,4) and are tangent to all three coordinate planes. How would I set that up? I have no problem finding the equation of a sphere when they give the center point and the radius, of course, but what do I need to know to find...
  17. M

    Calc 3 help. cross product

    thank you thank you. i was able to do the rest of the problems:) thanks again.
  18. M

    Calc 3 help. cross product

    I am having trouble setting this problem up. The problem says: Find a vector N that is perpendicular to the plane determined by the points P(0,1,0), Q(-1,1,2), R(2,1,-1), and find the area of triangle PQR. I know that the cross product of two vectors is perpendicular to the plane of a and b...
  19. M

    Helpfield of continuous distribution quest.

    I have been staring at this problem for an hour. I am not even sure where to start. A thin, circular disk of radius R is oriented in the xy-plane with its center at the origin. A charge Q on the disk is distributed uniformly over the surface. (a.) Find the electric field due to the disk at the...
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