Take a battery, two magnets of different sizes and intensities, small aluminium rod AB, connecting wires and an iron stand and arrange them as shown in the figure.
Now, bring the magnet with lower magnetic intensity closer to the aluminium rod. The rod deflects. Now observe the velocity of the rod. The displacement of the rod in the above activity suggests that a force is exerted on the current carrying conductor when it is placed in a magnetic field. Now steady the rod and bring both the magnets closer together to ensure that the magnetic field is stronger than before. The rod moves towards the magnet but faster than before. This is possible only if the force acting on the rod is stronger than before. Thus, the force acting on a current carrying conductor placed in a uniform magnetic field increases with increase in field strength.