GEOLOGY

Detailed explanation-1: -If a wire with a current with a continually reversing direction is placed between the poles of a magnetic the force will change the direction repeatedly. The force on a wire with a current in a magnetic field depends on the direction of the current. When the current is in one direction, the force would act downward.

Detailed explanation-2: -If the direction of the current is reversed, the compass needle will move in the opposite direction because the polarity of the magnetic field has reversed.

Detailed explanation-3: -On reversing the direction of current in a wire, the polarity of the faces of the wire also reverses. Thus, the direction of magnetic field produced by it also gets reversed and the correct choice is (a).

Detailed explanation-4: -If the forefinger points in the direction of the magnetic field and the middle finger in the direction of the current, then, the thumb points in the direction of the force exerted on the conductor.So, if the current is reversed in the conductor placed in a magnetic field the direction of force is also reversed.

Detailed explanation-5: -Answer: The magnetic field generated is always perpendicular to the direction of the current and parallel to the solonoid. Hence if we reverse the current the direction of magnetism also reverses.