Question

5. A current loop sits in the x ? y plane, centered on the origin. At the origin, the magnetic field due to the loop points in the positive z direction. What direction does the current in the loop run when viewed from the positive z direction?

(a) Counter-clockwise.

(b) Clockwise.

(c) The current is zero.
(d) More information is needed.

6. Two long conducting wires sit parallel to one another. The magnetic field at a point exactly half way between the two wires is measured to be zero. Which of the following statements could be true? (Choose all that could be true)

(a) The current through one wire is zero, but not both.

(b) The current through both wires is zero.

(c) The same current runs through both wires in the same direction.

(d) The same current runs through both wires in opposite directions.

7. Two long conducting wires set parallel to one another. The magnetic field at a point exactly one-quarter of the way between the two wires is measured to be non-zero. Which of the following statements could be true? (Choose all that could be true)

(a) The current through one wire is zero, but not both.

(b) The current through both wires is zero.

(c) The same current runs through both wires in the same direction.

(d) The same current runs through both wires in opposite directions.

8. A long straight wire lies on the y-axis. The wire sits in a uniform external magnetic field that points in the negative z direction. The net magnetic field at a point on the positive x axis is found to be zero, what can be said about the current in the wire?

(a) The current must be in the positive y direction.

(b) The current must be in the negative y direction.

(c) The current must be zero.

(d) This scenario is not possible.

9. A ferromagnet and electromagnet can be used together to

(a) Create a strong magnetic field.
(b) Create a weak magnetic field.
(c) Cancel any external magnetic fields.

(d) Create a heavy magnet.

10. A long straight wire lies on the z axis. The wire sits in a uniform external magnetic field that points in the negative

y direction. The net magnetic field at a point on the positive x axis is found to be zero, what can be said about the current in the wire?

(a) The current must be in the positive z direction.

(b) The current must be in the negative z direction.

(c) The current must be zero.

(d) This scenario is not possible.

Answer 1

5)
Using right hand screw rule, the current should flow in counter-clockwise direction for producing a magnetic field in the z-direction.

6)
If there is no current through any of the wires, there won't be any magnetic field.
If same current runs through both the wires in same direction, using right hand rule, one field is going into the page and the other is coming out of the page and the resultant is zero.
So options (b) and (c) are correct.

7)
Except for option (b), all others are correct.

8)
If the current is flowing in the negative y-direction, a magnetic field in the +z direction is created, which can be used cancel the magnetic field going in the - z-direction.
So, the answer is option (b)