Question

2. There are three wires carrying current. The direction of the currents for Wires 1 & 2 are as shown in the drawing to the right. The current in Wire 1, 11, is smaller than the current in Wire 2 (11 <12). At Point X, which is equidistant from all three wires, the magnetic field is zero. Wire 1 Wire 2 Wire 3 A) Determine the direction of the current in Wire 3 (13). Explain B) If Ti = 2A and 12 = 5A, what is the current in Wire 3? C) Determine the direction of the magnetic field at point Y, equidistant from both Wire 2 and Wire 3. Explain D) A positively charged particle Z is moving upward as shown. What is the direction of the force on Z from the magnetic field?

Answer 1

A) to the left.

at point X,

the direction of B1 is into the page

the direction of B2 is out of the page.

so, the direction of B2 - B1 is out of the page.

so, to make Bnet zero, the direction of B3 is into the page.

so, I3 direction is towards left.

B) I3 = I2 - I1

= 5 - 2

= 3 A

C) Into the page
at point Y, all the three wires produce magnetic field into the page.

D) direction of magnetic force is towards left.

Right hand rule: Take your right hand fingers in the direction of motion of positive charge and curl towards magnetic field then your thumb indicates the direction of magnetic force on the positive charge. For negative charge the direction opposite to the thumb gives the direction of magnetic force.