29. Sources of Magnetic Field

Two very long wires of unknown lengths are a parallel distance of 2 m from each other. If both wires have 3 A of current flowing through them in the same direction, what must the force per unit length on each wire be? 

BONUS:Is the mutual force between the wires attractive or repulsive?

Two long, parallel wires are separated by a distance of 0.400 m (Fig. E28.29). The currents I₁ and I₂ have the directions shown. Each current is doubled, so that I₁ becomes 10.0 A and I₂ becomes 4.00 A. Now what is the magnitude of the force that each wire exerts on a 1.20 m length of the other?

Two long, parallel wires are separated by a distance of 0.400 m (Fig. E28.29). The currents I₁ and I₂ have the directions shown. Calculate the magnitude of the force exerted by each wire on a 1.20-m length of the other. Is the force attractive or repulsive?

Four long, parallel power lines each carry 100 A currents. A cross-sectional diagram of these lines is a square, 20.0 cm on each side. For each of the three cases shown in Fig. E28.25, calculate the magnetic field at the center of the square.

A 175-g model airplane charged to 18.0 mC and traveling at 2.8 m/s passes within 7.8 cm of a wire, nearly parallel to its path, carrying a 25-A dc current. What acceleration (in g’s) does this interaction give the airplane?.

Two long, straight, parallel wires carry currents in the same direction. At point $z$, which is located exactly midway between the wires, what is the direction of the net magnetic field?

Which statement best describes what can be inferred about magnetic domains from the fact that they are arrangements of atoms?