1. See worked Griffiths example 5.4.
2. See worked Griffiths example 5.7.
3. See worked Griffiths example 5.9.
4. See worked Griffiths example 5.12.
5. 1. 
      

      

      The current induces a magnetic field that circles around it in a right-handed sense; that is, . As you have seen from Ampere's law (example 5.7 above), |B| varies radially, according to .

      For the pictured square Ampere loop, is pointing out of the paper with magnitude that varies within the loop. Note that the normal to the Ampere loop's surface also points out of the paper, provided we traverse it counterclockwise. Thus and integrating the flux gives

      

   2. If someone pulls the loop away from the wire at speed v, ds/dt = v. The flux through the square Ampere loop changes, with

      

      (I have used to make taking the s-derivative easy.) Thus an emf is generated, with

      

      The plus sign on the emf means that current flows counterclockwise about ; that is, since points out of the paper, counterclockwise.

      Let's check that this direction for the induced current makes sense, according to Lenz' law. Note that the flux decreases as s increases. Thus, as we pull the loop away from the wire, flux through it decreases, and the induced current opposes that decrease; that is, it creates its own positive flux. To create positive flux it must generate a positive field out of the page; thus, the induced current must flow counterclockwise, as we found.

   3. The flux of the loop depends only on s. Thus if someone pull the loop to the right at speed v, the flux remains unchanged. No emf is generated.
6. See worked Griffiths example 7.9.
7. See text, Griffiths p 322-324.

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