Question
Indicate whether the magnetic field created in each of the three situations shown in Figure 22.59 is into or out of the page on the left and right of the current.
Final Answer
- Left: Out of the page. Right: Into the page
- Left: Into the page. Right: Out of the page.
- Left: Into the page. Right: Out of the page.
Solution video
OpenStax College Physics for AP® Courses, Chapter 22, Problem 58 (Problems & Exercises)
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Video Transcript
This is College Physics Answers with Shaun Dychko. Using the right-hand rule, we are going to figure out whether the magnetic fields created by these moving charges is into or out of the page on the left and right side of these currents. So let's consider current (a): it's a conventional current with positive charge moving we presume and we will grab this wire with our right hand with our thumb pointing in the direction of current which is upwards and on the right hand side, our fingers will be pointing into the page and so that's the direction of magnetic field here into the page, which we can also indicate with x's. And then curling our hand around this wire, our fingers are coming out of the page on the left side so on the left side, the magnetic field is coming out of the page. Then in part (b), we use the right-hand rule again: our thumb will be pointing upwards but we have to notice that this is a negative charge that's moving and so the answers that we get from the right-hand rule, we have to take the opposite of those answers since the charge that's moving is negative. So whereas our thumb is pointing up and our fingers are pointing into the page on the right hand side just as they were for part (a), we now have to say that the magnetic field is in fact coming out of the page since these are negative moving charges and so the answers are opposite to our right-hand rule. And then curling our fingers around, our fingers come out of the page but we interpret that as magnetic field going into the page nevertheless since the charge is negative. Okay! And then for part (c), we have a conventional current or positive charge is moving in other words, we grab this with our right hand but our thumb is pointing down now and our fingers go into the page on the left or sorry... x's for into the page and then curling our hand around, we have the fingers coming out of the page on the right hand side so on the right hand side is out of the page. There we go!