PHYS 2212 Module 8.4

Magnetic Force between Two Parallel Currents

Recommended Reading

8.4 Magnetic Force between Two Parallel Currents

Learning Objectives

By the end of this section, you will be able to:

  • Explain how parallel wires carrying currents can attract or repel each other
  • Define the ampere and describe how it is related to current-carrying wires
  • Calculate the force of attraction or repulsion between two current-carrying wires

Magnetic Force Between Wires

Practice!

Practice 8.4.1
You have two parallel wires carrying currents in the same direction.

What is the direction of the magnetic field that is created by I1 at the position where I2 is located?
Check your answer: F. Out of the page
Practice 8.4.2
You have two parallel wires carrying currents in the same direction.

What is the direction of the magnetic force due to I1 that acts on I2?
Check your answer: B. Upward
Practice 8.4.3
In the two situations there are two parallel wires carrying current in opposite directions (A) and in the same direction (B). What will happen to the wires?
Check your answer: B. The wires in (A) will repel and the wires in (B) will attract.
Practice 8.4.4
A current I flows in the +y direction in an infinite wire. A current I also flows in the loop as shown. What is Fx, the net force on the loop in the x-direction?
Check your answer: A. F_x points to the left

Discuss!

The long, straight wire AB carries a 14.0-A current as shown. The rectangular loop has long edges parallel to AB and carries a clock- wise 5.00-A current. What is the net magnetic force that the straight wire AB exerts on the loop?