Magnetic Field around a Circular Wire
Circular wire produces magnetic field inside the circle and outside the circle. Magnetic field around a circular wire is calculated by the formula;
B=2πk.i/r
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Direction of the magnetic field at the center of the circle is found with right hand rule.
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Your thumb shows the direction of magnetic field and four fingers show direction of current. Moreover, we can show the direction of current inside the circle with following pictures;
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Example: Find the magnitude and direction of magnetic field at the center of the semicircle given below.
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When we apply right hand rule we see that direction of magnetic field is inward to the page as shown in the picture below, since we have semicircle, we put 1/2 in front of our formula;
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Example: Directions of i1 and i2 currents are opposite. If the magnetic field at the center of the circles is zero find the ratio of i1 to i2 i1/i2?
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Smaller circle has magnetic field ;
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Example: Find the magnetic field produced by currents i1 and i2 at point O.
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If we apply right hand rule, directions of currents are;
i1:inward
i2:outward
Thus, total magnetic field at point O becomes the difference of these magnetic fields.
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