. 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. (b) 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?

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.

Two long parallel wires lie in the x-y plane, and each carry $5.0\mathrm{A}$ currents in opposite directions. Wire 1 lies along the $y=3.0\mathrm{cm}$ line and carries a current in the positive x direction; wire 2 lies along the y = 0$y=0$ line and carries a current in the negative x direction. What is the magnitude of the magnetic field at the point ($0\mathrm{cm}$, $1.5\mathrm{cm}$, $0\mathrm{cm}$)?

Two long parallel wires lie in the x-y plane, and each carry $5.0\mathrm{A}$ currents in opposite directions. Wire 1 lies along the $y=3.0\mathrm{cm}$ line and carries a current in the negative x direction; wire 2 lies along the $y=0$ line and carries a current in the positive x direction. What is the direction of the magnetic field at the point ($0\mathrm{cm}$, $0\mathrm{cm}$, $1.5\mathrm{cm}$)?

. 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. (a) 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.