Final answer:
The term for magnetic forces deflecting an arc from its path is known as arc blow, which is a consequence of the pinch effect.
Step-by-step explanation:
When magnetic forces deflect the arc from its intended path, the action is called arc blow. This is due to the pinch effect where the magnetic fields generated by the currents moving through the arc cause it to contract and sometimes be deflected. This effect is crucial in understanding how currents behave in various situations, from electrical welding to solar flares and the operation of large circuit breakers in power distribution systems.