Magnetic fields resemble electric fields in many ways. A common misconception am

Question

Magnetic fields resemble electric fields in many ways. A common misconception among students first learning about magnetic fields is that a magnet is just an electric dipole (a positive charge near a negative charge), with the positive charge at the north end and the negative charge at the south end. What is a simple piece of experimental evidence that demonstrates that magnetic forces are different from electric forces (i.e that magnetic poles are not electric charges)? In the first diagram of "An atlas of magnetic fields produced by a wire" we see a drawing of the magnetic field around a straight wire. Use the right hand rule to determine whether the current in that diagram is into or out of the page. The diagram at right shows two wires with currents, labeled I1 and I2, coming out of the page. At point a draw and label the vectors, B1 and B2, representing the magnetic fields at a due to I1 and I2. If I1 and I2 are identical then what is the total magnetic field at point a? Now at point b draw and label the vectors, B1 and B2, representing the magnetic fields at b due to I1 and I2. The diagram at left shows a positively charged particle moving parallel to the x-axis. It is moving through a region in which the magnetic field points into the page as indicated in the diagram. What is the direction of the magnetic force on the particle? The diagram at left shows a wire carrying current to the right. What is the direction of the magnetic field at point A? If a proton (positively charged) passes through point A moving to the light what will be the direction of the magnetic force on the proton?

Explanation / Answer

1) magnetic dipoles are different from electric dipoles as they always exist in pair, or there is no existence of magnetic monopole

If we cut a magnet then also it has North and South poles, and not only north or south pole

2) the magnetic field direction can be found out by finding out the cross product of current and radius vector r (distance of point)

.ie I x r

so at point a

B1 = in upward direction

B2 = in downward direction

if I1 and I2 are same i.e. I

then net magnetic field at a = Bnet = B1 - B2

if a is the mid poiint here then B1 = B2 then Bnet = 0

3) here both the current carrying conductors lie on the same side hence their direction of Induced magnetic field will be same

Bnet = B1 + B2 in upward direction

4) we knoe that

F = q (VxB)

so the direction of force can be found out by evaluating the cross product of V and B

which is in the upward direction

5)again we know that the direction of inducecd magnetic field can be found out by cross product of current and direction vector of point

i.e . I x r

which gives into the paper direction

6) it is the same cas as a) so force will be acting upward direction

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