Use the gradient of Figure 1 to determine the magnetic field strength.

A separate straight wire segment of length $0.12\ \mathrm{m}$ carries a current of $1.5\ \mathrm{A}$ due east in a uniform magnetic field directed vertically upwards. The wire is perpendicular to the magnetic field. Use your answer to (a) to calculate the magnitude of the force on the wire and state its direction.

Two long parallel wires carry currents of $4.0\ \mathrm{A}$ and $6.0\ \mathrm{A}$ in the same direction. Their separation is $0.050\ \mathrm{m}$ Calculate the force per unit length between the wires and state whether the force is attractive or repulsive.

Use $\mu_0=4\pi\times10^{-7}\ \mathrm{N\,A^{-2}}$