The figure below shows a long straight wire just touching a loop carrying a curr

Question

The figure below shows a long straight wire just touching a loop carrying a current I1. Both lie in the same plane.

Q:What direction must the current I2 in the straight wire have to create a field at the center of the loop in the direction opposite to that created by the loop?

2 options

1.NE to SW or 2.SW to NE

Q:What is the ratio of I1/I2 that gives zero field strength at the center of the loop?

Q:What is the direction of the field directly above the loop under this circumstance?
Field above loop

The figure below shows a long straight wire just touching a loop carrying a current I1. Both lie in the same plane. Q:What direction must the current I2 in the straight wire have to create a field at the center of the loop in the direction opposite to that created by the loop? 2 options 1.NE to SW or 2.SW to NE Q:What is the ratio of I1/I2 that gives zero field strength at the center of the loop? Q:What is the direction of the field directly above the loop under this circumstance? Field above loop ?? 7 options N, E, S, W, out of page, into page, no field

Explanation / Answer

!)

Using Right Hand Thumb rule, we see that the current in the loop produces Magnetic field out of the plane of the loop.

Thus current in the wire must be such that its magnetic field must be directed into the plane.

For this to happen again applying Right Hand Thumb rule to this wire, the current must be directed from the North East(NE) towards South West(SW)

So, answer is NE to SW <-----------

2)

Magnetic field due to the loop is given by : Bl = u*I1/(2*R)

where u = 1.26*10^-6

Now, Magnetic field due to the wire, Bw = u*I2/(2*pi*R)

For the field strength at the center to be 0,

Bw = Bl

So, u*(I1)/(2*R) = u*(I2)/(2*pi*R)

So, I1/I2 = 1/pi = 0.318 <-------------answer

3)

Directly above the loop Magnetic field due to loop , Bl' = u*R^2*I1/(2*(z^2+R^2)^(3/2))

In this case, I2 = pi*I1

So, Bl' = u*R^2*(I2*pi)/(2(z^2+R^2)^(3/2))

for the wire, Bw' = u*I2/(2*pi*sqrt(R^2+z^2))

Now, we can clearly that Bw' is slightly greater than Bl', So, Bw' will dominate and the resultant magnetic field will be directed towards the direction of Bw' which is into the page <--------answer

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.