Chapter 20. Magnetic flux (20-1)

Question

G8Asc/Cw6P5HJSLNwLl+S38WasKq4mnt4+FPtoXdzGBjyzkTbzMlCOyxb5rfMjApg2DmwA==
{"title":"Magnetic flux through a surface","description":"Correct!","type":"correct","color":"#99CCFF","code":"[{\"shape\":\"poly\",\"coords\":\"82,133\"},{\"shape\":\"rect\",\"coords\":\"10,16,12,16\"},{\"shape\":\"poly\",\"coords\":\"144,22\"},{\"shape\":\"rect\",\"coords\":\"1,2,25,34\"}]"} {"title":"Area of the surface","description":"Wrong","type":"incorrect","color":"#ffcc00","code":"[{\"shape\":\"rect\",\"coords\":\"77,5,100,32\"},{\"shape\":\"rect\",\"coords\":\"172,5,196,33\"}]"} {"title":"Angle between the magnetic field and the perpendicular to the surface","description":"Incorrect","type":"incorrect","color":"#333300","code":"[{\"shape\":\"rect\",\"coords\":\"281,5,300,31\"}]"} {"title":"Magnitude of the magnetic field","description":"Incorrect","type":"incorrect","color":"#000080","code":"[{\"shape\":\"rect\",\"coords\":\"199,5,218,32\"}]"} {"title":"The component of magnetic field perpendicular to the surface","description":"Incorrect","type":"incorrect","color":"#333333","code":"[{\"shape\":\"rect\",\"coords\":\"101,5,122,32\"}]"}

Question

y09IsKyCqqdPnaX/oGzKNHavI/hxIo1j
{"title":"Magnetic flux through a surface","description":"Incorrect","type":"incorrect","color":"#99CCFF","code":"[{\"shape\":\"poly\",\"coords\":\"82,133\"},{\"shape\":\"rect\",\"coords\":\"10,16,12,16\"},{\"shape\":\"poly\",\"coords\":\"144,22\"},{\"shape\":\"rect\",\"coords\":\"1,2,25,34\"}]"} {"title":"Area of the surface","description":"Correct!","type":"correct","color":"#ffcc00","code":"[{\"shape\":\"rect\",\"coords\":\"77,5,100,32\"},{\"shape\":\"rect\",\"coords\":\"172,5,196,33\"}]"} {"title":"Angle between the magnetic field and the perpendicular to the surface","description":"Incorrect","type":"incorrect","color":"#333300","code":"[{\"shape\":\"rect\",\"coords\":\"281,5,300,31\"}]"} {"title":"Magnitude of the magnetic field","description":"Incorrect","type":"incorrect","color":"#000080","code":"[{\"shape\":\"rect\",\"coords\":\"199,5,218,32\"}]"} {"title":"The component of magnetic field perpendicular to the surface","description":"Incorrect","type":"incorrect","color":"#333333","code":"[{\"shape\":\"rect\",\"coords\":\"101,5,122,32\"}]"}

Question

V5tLsH8Uv6TVA999LGjnQq7ydCt60jzScUm9kjf2548xiMF8tyQuMJAqoa4oC8mBq8VzTzVDAhnQNbsP9sDyZRcVsbRH1Y3zJC9f2w==
{"title":"Magnetic flux through a surface","description":"Incorrect","type":"incorrect","color":"#99CCFF","code":"[{\"shape\":\"poly\",\"coords\":\"82,133\"},{\"shape\":\"rect\",\"coords\":\"10,16,12,16\"},{\"shape\":\"poly\",\"coords\":\"144,22\"},{\"shape\":\"rect\",\"coords\":\"1,2,25,34\"}]"} {"title":"Area of the surface","description":"Incorrect","type":"incorrect","color":"#ffcc00","code":"[{\"shape\":\"rect\",\"coords\":\"77,5,100,32\"},{\"shape\":\"rect\",\"coords\":\"172,5,196,33\"}]"} {"title":"Angle between the magnetic field and the perpendicular to the surface","description":"Correct!","type":"correct","color":"#333300","code":"[{\"shape\":\"rect\",\"coords\":\"281,5,300,31\"}]"} {"title":"Magnitude of the magnetic field","description":"Incorrect","type":"incorrect","color":"#000080","code":"[{\"shape\":\"rect\",\"coords\":\"199,5,218,32\"}]"} {"title":"The component of magnetic field perpendicular to the surface","description":"Incorrect","type":"incorrect","color":"#333333","code":"[{\"shape\":\"rect\",\"coords\":\"101,5,122,32\"}]"}

Question

BxwqFElCMrv6osRQIzwEy9NfZ7O5DiHi8cUDjelh1iClRv7W
{"title":"Magnetic flux through a surface","description":"Incorrect","type":"incorrect","color":"#99CCFF","code":"[{\"shape\":\"poly\",\"coords\":\"82,133\"},{\"shape\":\"rect\",\"coords\":\"10,16,12,16\"},{\"shape\":\"poly\",\"coords\":\"144,22\"},{\"shape\":\"rect\",\"coords\":\"1,2,25,34\"}]"} {"title":"Area of the surface","description":"Incorrect","type":"incorrect","color":"#ffcc00","code":"[{\"shape\":\"rect\",\"coords\":\"77,5,100,32\"},{\"shape\":\"rect\",\"coords\":\"172,5,196,33\"}]"} {"title":"Angle between the magnetic field and the perpendicular to the surface","description":"Incorrect","type":"incorrect","color":"#333300","code":"[{\"shape\":\"rect\",\"coords\":\"281,5,300,31\"}]"} {"title":"Magnitude of the magnetic field","description":"Correct!","type":"correct","color":"#000080","code":"[{\"shape\":\"rect\",\"coords\":\"199,5,218,32\"}]"} {"title":"The component of magnetic field perpendicular to the surface","description":"Incorrect","type":"incorrect","color":"#333333","code":"[{\"shape\":\"rect\",\"coords\":\"101,5,122,32\"}]"}

Question

FgUJtRADYQxf9xTyjzrSoLL0VuIYxWITGPZ8lwFm5pzplDsZMnH0pivkGbXWUIAq1xsFsKL7sePe7S6POFayqQ==
{"title":"Magnetic flux through a surface","description":"Incorrect","type":"incorrect","color":"#99CCFF","code":"[{\"shape\":\"poly\",\"coords\":\"82,133\"},{\"shape\":\"rect\",\"coords\":\"10,16,12,16\"},{\"shape\":\"poly\",\"coords\":\"144,22\"},{\"shape\":\"rect\",\"coords\":\"1,2,25,34\"}]"} {"title":"Area of the surface","description":"Incorrect","type":"incorrect","color":"#ffcc00","code":"[{\"shape\":\"rect\",\"coords\":\"77,5,100,32\"},{\"shape\":\"rect\",\"coords\":\"172,5,196,33\"}]"} {"title":"Angle between the magnetic field and the perpendicular to the surface","description":"Incorrect","type":"incorrect","color":"#333300","code":"[{\"shape\":\"rect\",\"coords\":\"281,5,300,31\"}]"} {"title":"Magnitude of the magnetic field","description":"Incorrect","type":"incorrect","color":"#000080","code":"[{\"shape\":\"rect\",\"coords\":\"199,5,218,32\"}]"} {"title":"The component of magnetic field perpendicular to the surface","description":"Correct!","type":"correct","color":"#333333","code":"[{\"shape\":\"rect\",\"coords\":\"101,5,122,32\"}]"}

Review

It turns out that a simple way to describe the emf in any of these situations is in terms of the change in magnetic flux through the loop in Figures 20-2 and 20-3. We define this in the same way that we defined electric flux in Section 16-6: It’s the area \(A\) of the surface outlined by the loop, multiplied by \(B \cos{\theta}\), the component of the magnetic field that’s perpendicular to that surface (see part (a) of Figure 20-4). In equation form, the magnetic flux \(\Phi_B\) (“phi-sub-B”) through the loop is

(The subscript \(B\) reminds us that this is the flux of the magnetic field \(\vec{B}\).) As parts (b) and (c) of Figure 20-4 show, the flux \(\Phi_B\) can be positive or negative.