Magnetic Fields

Question 1

A group of students is investigating whether a magnetic field exists between two magnets that are not touching. They place a north‑pole magnet on a table, hold a second north‑pole magnet on a spring scale, and record the force on the scale as they move the magnets farther apart. Which change to the experimental design would provide the strongest additional evidence that a field, not contact, is responsible for the force?

Accepted Answer

Insert a thin piece of non‑magnetic wood between the two magnets and still measure a force on the second magnet.

Answer

Replace the magnets with heavier, non‑magnetic metal blocks of the same size.

Answer

Place the two magnets in direct contact and record the force reading.

Answer

Use a metal ruler to measure the distance between the magnets instead of a plastic ruler.

Question 2

A group of students wants to investigate whether a magnetic field can exert a force on a paperclip without the two objects touching. They set up the following procedure: (1) Hang a paperclip from a thin string so it can swing freely. (2) Place a bar magnet directly below the hanging paperclip. (3) Observe whether the paperclip moves toward the magnet. (4) Replace the magnet with a piece of wood of the same size and repeat the observation. Which observation best shows that the experimental design provides evidence that a field exists between the magnet and the paperclip even though they are not in contact?

Accepted Answer

The paperclip moves toward the magnet while hanging from the string, and it does not move when the magnet is replaced by the wood piece.

Answer

The paperclip is pulled directly by the string when the magnet is placed next to it.

Answer

The magnet is heated and the paperclip melts, showing interaction.

Answer

The paperclip is placed on the table and slides toward the magnet when the table is tilted.

Question 3

A student designs an experiment to test whether a magnetic field can exert a force on a current‑carrying wire without any contact. The wire is placed between the north and south poles of a bar magnet, and a battery is connected so that current flows from left to right. The wire moves upward. To further investigate, the student reverses the direction of the current while keeping the magnet in the same position. Which observation would best support the conclusion that the magnetic field—not contact forces—is causing the wire’s motion?

Accepted Answer

The wire moves downward when the current direction is reversed, even though the wire remains the same distance from the magnet.

Answer

The wire moves upward only when the magnet is physically touched by the wire, suggesting that contact is required for the force.

Answer

The wire continues to move upward after the current is reversed, showing that the magnetic field exerts a constant upward force regardless of current direction.

Answer

The wire stops moving when the current is reversed, indicating that the force depends on the direction of current.

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