{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Fall 2011 Homework 14 Solutions

Fall 2011 Homework 14 Solutions - Physics 21 Fall 2011...

Info icon This preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Physics 21 Fall, 2011 Solution to HW-14 Cancelling Magnetic Field Four very long, current- carrying wires in the same plane intersect to form a square with side lengths of 39.0 cm, as shown in the figure. The cur- rents running through the wires are 8.0 A, 20.0 A, 10.0 A, and I . Find the magnitude and direction of the current I that will make the magnetic field at the center of the square equal to zero. The field point at the center of the square is equidistant from all four wires. Let this distance be d = 1 2 × 0 . 39 m. We just have to keep track of the direction of each field using the right hand rule. Let out of the page be plus, and let I > 0 correspond to up: B out of page = μ 0 2 πd ( - 10 + I - 8 + 20) Solving, we get I = - 2 A, and the minus sign means I is directed downward. 28-22 Two long, parallel transmission lines, L = 38 . 0 cm apart, carry currents I 1 = 23 . 0-A and I 2 = 78 . 0-A. Find all locations where the net magnetic field of the two wires is zero if these currents are (a) in the same direction or (b) in opposite directions. (a) (b) L x L x I 1 I 2 I 2 I 1 (a) Panel (a) of the diagram shows the two wires end on when the currents are in the same direction. L is the distance between the wires. The magnetic field lines due to each wire separately are shown by the concentric circles (dashed for I 1 , solid for I 2 ). The direction of the field follows from the right hand rule and is shown at selected points by an arrow next to each circle. By looking at the directions of the two fields in various locations, it’s easy to see that for case (a), the vector sum of the fields can only be zero on the line between the wires. The magnitude of the field B a distance R from a long wire with current I is B = μ 0 I/ (2 πR ). The vector field will be zero at a point on the line between the wires a distance x from the left wire and L - x from the right wire, where the magnitudes of the fields are equal. Then
Image of page 1

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

View Full Document Right Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    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.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    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.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    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.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern