IB Physics Why is the magnetic force perpendicular to the current?

Why does the magnetic force on a current push perpendicular to the conductor? The magnetic field direction around a straight wire carrying a current in a uniform external magnetic field is shown below. The current is flowing out of the page and the uniform magnetic field direction is to the right. The diagram shows the resultant magnetic field found by adding the magnetic field created by the current and the uniform magnetic field. Magnetic field lines can be thought of as exerting a tension along their length and a pressure perpendicular to their length, like elastic bands. What does the diagram suggest about the direction of the magnetic force acting on the current? Upwards, in agreement with the right hand palm rule.