can anyone explain the activity 13.7

I am just providing you hint for this activity.In case of any doubt you can get back to us.The rod get displaced due to the fact that when we pass current through the rod , then magnetic field get developed around it.Also we know that like poles repel each other.So when south pole of the magnet and rod are towards each other so due to this property they get replled.Hence rod get displaced towards right.Similarly when we change the direction of the current in the rod then its poles are also get changed with respect to the previous one , So direction of displacement of the rod will also get changed.