As long as they are cleared to play if injured they can return
he is not injured
As long as there is nothing in the player's contract that forbids it, a player can be traded while on injured reserve. I can say that I can't remember that ever happening but it is within the rules since the team trading for the player would know of the injury.
Yes. As long as the field player is in possession range of the ball, the player can shield. However, if the player is not within possession range of the ball and tries to shield, he will be called for obstruction.
The answer is is yes, as long as they player does not touch it with his hands.
It will not remain "charged" for long. The speed of collapse of the magnetic field is related to the inductance, in Henries. A (physically) large inductor will retain energy for longer. (note that there is no "charge")
Electric field is got by the expression = charge density / epsilon not As so long charges on the plate remain the same the electric field also remains the same
If on offense they have 3 seconds in the key, if on defense they can stay as long as they like.
It becomes an Equip Card when it resolves, and as such, will remain on the field until it loses its target - like if the equipped monster is flipped face-down or leaves the field.