A260-m length of wire stretches between two towers and carries a 115-a current. determine the magnitude of the force on the wire due to the earth's magnetic field of 5.0 ×10−5t which makes an angle of 80 ∘ with the wire.

The force exerted by a magnetic field of intensity B on a wire of length L is:

where I is the current in the wire and  is the angle between the wire and the direction of B.
In our problem, the length of the wire is L=260 m, the current is I=115 A, the intensity of the Earth's magnetic field is  and the angle between the wire and B is , and by substituting these numbers in the previous expression we can find the magnitude of the force: