a. the moving charge induces a magnet field.
b. the energy of the charge pushes on the compass.
c. the electrons heat up the wire, causing the compass to deflect.
+ and – attract each other, therefore there is a flow of electrons from the – end to the + end. Magnet fields are caused if there is a misbalance between + and – charge. If you rub a plastic stick on a fur (use your cat – works perfectly) and then hold it close to a thin water stream from the water tap, it will make the water move toward the stick. That is because the stick carries a negative charge and water is a dipole (2 positive atoms, one negative). So that is the same principle as in magnet fields.
The moving charge induces a magnet field.