Question

1. the image shows an electromagnet made by wrapping a coil of wire around an iron nail and connecting it to a battery.

a student observes that the electromagnet is generating a weak magnetic field. which of these changes would most effectively strengthen the magnetic field and improve the device’s ability to generate electrical energy?

• increasing the voltage of the battery used in the circuit.
• using a shorter length of wire for the coil around the nail.
• replacing the iron nail with a wooden dowel to reduce resistance.
• reducing the number of coils around the nail to create a more compact setup.

Explanation:

To strengthen an electromagnet's field, we analyze each option:

• Increasing battery voltage increases current, which strengthens the magnetic field (since \( B \propto I \) for electromagnets).
• A shorter wire length might increase current, but the primary factor for electromagnet strength is current, number of coils, and core material. However, "increasing voltage" is a direct way to boost current ( \( V = IR \), so higher \( V \) with constant \( R \) gives higher \( I \)).
• Replacing the iron nail (a ferromagnetic core) with wood (non - magnetic) weakens the field, as ferromagnetic cores concentrate magnetic flux.
• Reducing the number of coils decreases the field ( \( B \propto N \), where \( N \) is the number of turns).

Answer:

Increasing the voltage of the battery used in the circuit.