Final answer:
To increase the strength of a magnetic field created by a current in a wire, the wire should be wrapped into a coil, as this multiple layering of wire compounds the magnetic effects within the coil.
Step-by-step explanation:
The strength of a magnetic field created by current in a wire can be increased by wrapping the wire into a coil. This is because coiling the wire adds multiple layers of current-carrying wires, which amplifies the magnetic field inside the coil, following Ampère's Law. Each loop of wire in the coil can be thought of as a small magnet, and when you add these together, they create a stronger overall magnetic field. Decreasing the current in the wire would weaken the magnetic field, not strengthen it. Using longer or shorter wire without forming a coil does not change the strength of the magnetic field produced by a specified current in the wire.
Moreover, to address a related concept, an induced current in a wire loop through which a magnetic field passes can be created by changing the strength of the magnetic field, changing the size of the wire loop, or changing the orientation of the wire loop, according to Faraday's Law of Electromagnetic Induction.