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# Three loops of wire move near a long straight wire carrying a current as in Figure P20.9. What is the direction of the induced current, if any, in (a) loop A, (b) loop B, and (c) loop C.

## a. zero b. \text { counter clockwise }c. \text { clockwise }

### Discussion

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##### Christina K.

Rutgers, The State University of New Jersey

##### Andy C.

University of Michigan - Ann Arbor

##### Marshall S.

University of Washington

### Video Transcript

All right, So Ah, here. You have a long loop. Hi. Okay. Carrying current pie, you have, uh, three loops this long, white can can I and three loops beside it. One slip a going parallel e up a lot of wire up. Ah, Luke Be which is going to the left. Ah, and loops. See which is going to the right. Um and so we have to figure out the direction of the induced current, if any, and port A As you can see. Ah, the motion of the wire is parallel to the loop. So there's no India's current. You gotta have an angle between the loop and the magnetic field. That's not happening. Um, right. And so no induced current er and part dealing. What you have is s O. What's going on here is that the magnetic field loops around like this, right? So that's a boo. Are, uh that's being so here, your fields trying to announce a mother. So your field strength out of the carriage is actually decreasing, and these will denote out of Paige. Your field strength is decreasing when you're moving further away from the loop, eh? So what you want by lenses law. Is that your field strength? I should go up out of the page. Ah, to counteract this change on. In order for that to happen, you've looped. Use the right handle on What you find is that, um in order to increase your magnetic field cup of out of coming out of Paige, you have Ah, you have to have, uh, your current pointing now like that. And so it will be pointing counter clockwise. So that's I That's I That's I So, uh, part B is counterclockwise, uh, current. And what's happening in part silly, is that Kurt is moving out of the period coming out of the periods dinner by these access here. And as the loop moves away from the from the wire, the magnetic field will Deke of my God, felines coming out of the page will decrease. So buy lenses law. You want my fear lines to increase coming out of the page. Eso again by right hand rule. We noticed that, uh, you know, in order for this condition to be satisfied, you have, um, you'll have a magnetic. Now you have a magnetic. Uh, you'll have an induced current. That is that acts in this direction. So this is clockwise. So part of you is clockwise. The current has opposed to counter clockwise and part. You have clockwise and part. See, look. See? That's it.

New Mexico State University
##### Christina K.

Rutgers, The State University of New Jersey

##### Andy C.

University of Michigan - Ann Arbor

##### Marshall S.

University of Washington