Question

manipulating the strength of an electromagr
simple electromagnet
predict what would
electromagnet in e
using a battery wit
weaker force of a
wrapping the wire
weaker force of a
changing the direction of the current by reversing the
battery connections:
using a plastic stick in place of the iron nail:
holding the nail vertically rather than horizontally:

Explanation:

Changing the direction of the current by reversing the battery connections

The strength of the electromagnet depends on the magnitude of the current and the number of turns in the coil, not on the direction of the current. So, reversing the battery connections (which changes the current direction) will have no effect on the force of attraction.

Using a plastic stick in place of the iron nail

An electromagnet works because the iron nail (a ferromagnetic material) gets magnetized when current passes through the coil. Plastic is not a ferromagnetic material. So, using a plastic stick will result in a weaker force of attraction (in fact, almost no magnetic attraction as plastic does not support the formation of a strong magnetic field like iron does).

Holding the nail vertically rather than horizontally

The orientation (vertical or horizontal) of the nail does not affect the magnetic properties related to the current - coil - nail system. The magnetic field around the coil - nail (when current is on) is determined by the current and the coil - nail setup, not by the orientation of the nail in space (assuming no external magnetic field effects due to Earth's magnetism in a significant way for a simple electromagnet setup). So, there is no change in the force of attraction.

Answer:

Changing the direction of the current by reversing the battery connections: no change; Using a plastic stick in place of the iron nail: weaker force of attraction; Holding the nail vertically rather than horizontally: no change.