## Lecture 6: Ampere's Law

February 1, 2018

• Study: Eq 26.17; Exs. 26.7, 26.8, 26.9; Fig 26.34

### Objectives

• (Continuing objective) Describe applications of the concepts of electricity and magnetism to everyday real-life'' situations.
• Distinguish and correctly use the expressions for the magnetic field for each of these special situations: (a) at the center of a circular loop or finite arcs of a circular loop; (b) inside and just outside the central region of a very long solenoid, (c) outside a wire segment or long straight wire. Use these and superposition to find the total B-field due to a combination of sources.
• Use Ampere's Law to relate the loop integral of $\vec{B}$ (circulation) to the net encircled current.
• Use Ampere's Law to calculate the magnetic fields due to symmetric steady currents.

### Homework

• Friday's Assigned Problems: A21, A22, A111; CH 26: 11, 37, 65, 67, 71, 75;

NOTE: Error in A111. For part (c), it should be 2.5 mm, not 5.0 mm. Answer for A111: a) 0.10 mT; b) 0.20 mT; c) 0.1 mT.

• Monday's Hand-In Problems: CH 26: 32, 36, 38, 54, 62, 66, 68, 70, 76, 80

Notes: For CH 26 #62, sketch the end-on view so 3 wires are shown as dots in an equilateral triangle, each carrying current out of the page. First find B at the top wire DUE to currents in the other two wires. (You can assume the field from each wire as though the wire were infinitely long.) Then find the force.

### Videos of example problems

To see the problem statement, click on the link below. To play the video example, click on the underlined words "Video Demonstration" near the top of the page with the problem statement.