Final answer:
The straight wire antenna of a radio should be vertical to receive radio waves broadcast by a vertical transmitter antenna. A loop antenna should be aligned horizontally to receive the signals.
Step-by-step explanation:
To best receive radio waves broadcast by a vertical transmitter antenna, the straight wire antenna of a radio should be vertical. This is because radio waves are electromagnetic waves that have an electric field component and a magnetic field component. The electric field of a vertically transmitted radio wave is aligned vertically, so a vertical wire antenna can interact more efficiently with the electric field.
On the other hand, a loop antenna should be aligned horizontally to best receive the signals. A loop antenna consists of a loop of wire rather than a straight wire. Its orientation should be aligned perpendicular to the direction of the magnetic field component of the radio waves for optimal reception.
An example of a loop antenna used for signal reception is in nature studies, where it can be used to track tagged animals by determining the direction that produces the best reception, thus indicating the location of the source.