A wire carries a current 5 A. The wire comes in straight from far away until it

Question

A wire carries a current 5 A. The wire comes in straight from far away until it reaches a distance 50 cm from a certain point P, arcs around at a constant distance from that point, and then exits straight out at the angle of 90o from the incoming direction. Consider the magnetic field at the point P.

(a) What is the contribution to the magnetic field in P from the long straight sections?
1
0T (Don't understand why it's 0, missing something conceptually here)

(b) Use the Biot-Savart law to calculate the magnitude of the magnetic field in P.
2

1.57e-06(this is correct-need explanation)

0(got it wrong first time, explain why 0 please? I'm missing something conceptually

Explanation / Answer

For those who stumble across this in the future, I figured it out. Part A is 0 because in the Biot-Savart law the change in l and the direction vector r(not the radius, that exists too) are parallel(they need to be at an angle or perpendicular- they are parallel/overlapping). If you trace the current across the wire, but ignore the curve and make the full 90 degree bend, the Sin(0) element of the equation will make it 0. Part B the change in l is equivalent to (1/4)2pi(radius) aka 1/4 the circumference. Plug that in for l, and use the Biot-Savart law as normal.

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

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