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A student wraps insulated copper wire 12 times around a nail, and connects the ends to a fresh 9-volt battery. The student finds that the nail can now be used to lift small iron weights. The student disconnects the circuit and wraps a longer copper wire 30 times around another nail of the same type. The student then connects the wire to a fresh 9-volt battery. What should the student observe when attempting to use the new nail to lift small iron weights?

A. The nail will be able to lift heavier weights, because the greater number of turns of the wire yields a more powerful magnetic field.
B. The nail will be able to lift heavier weights, because the greater mass of conductive matter in the system will balance a greater mass of iron in the weights.
C. The nail will only be able to lift the same amount of weight, because the magnetic force of the system depends on the current from the battery, which has not changed.
D. The nail will only be able to lift the same amount of weight, because the physical properties of the nail determine magnetic force, and nails of the same type were used in both trials.

1 answer

In this scenario, the key factor affecting the lifting capability of the nails wrapped in copper wire is the number of turns of the wire, which influences the strength of the magnetic field generated around the nail when current flows through the wire.

The magnetic field intensity generated by a solenoid-like configuration (the copper wire wrapped around the nail) is proportional to both the number of turns of wire and the current flowing through it. In this case, while the battery voltage remains the same, the increase in the number of turns (from 12 to 30) will lead to a stronger magnetic field around the nail.

Based on this understanding:

A. The nail will be able to lift heavier weights, because the greater number of turns of the wire yields a more powerful magnetic field.

This is the most accurate observation, as the increased number of turns increases the magnetic field strength, thereby enhancing the lifting capability of the nail to lift heavier weights.