To increase the strength of the magnetic field of a coiled electrical wire, you can:
- Adding more coils to the wire: Increasing the number of coils (or turns) will enhance the strength of the magnetic field, as the magnetic field contributions from each loop add together.
Straightening the wire, changing the direction of the current flow, and stopping the current do not increase the strength of the magnetic field. In fact, stopping the current would eliminate the magnetic field altogether. Changing the direction of the current would reverse the direction of the magnetic field but does not increase its strength.
So, the correct answer is: adding more coils to the wire.