For an ideal solenoid, the interior magnetic field is uniform and the exterior field is zero.
a. true
b. false

true

Explanation:

The magnetic field inside the solenoid is uniform if the solenoid is ideal.

Outside the solenoid, the magnetic field is zero.

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the answer is the first electromagnet (a). this is because it has more coils around the ferromagnetic material. increasing the number of coils increases the surface area in which the metal interacts with the current in the coil. this enables more atoms in the metal to become aligned hence becoming more magnetized.