The strength of an electromagnet increases with

Analyze the question: The question asks which change makes an electromagnet stronger.

Concept: The strength of an electromagnet depends on:

• The number of turns of the coil (more turns means a stronger magnetic field)
• The current flowing through the coil (more current means a stronger field)
• The core material (a soft iron core strengthens the field)

For a solenoid, the magnetic field is B = μ₀nI, where n is the number of turns per unit length and I is the current. So B increases when n or I increases.

Check each option:

• A. Increases in the number of turns of the coil. Correct. A larger n gives a larger B, so the magnet is stronger.
• B. Decreases in current with the coil. Wrong. Less current means a weaker field.
• C. Increases in the distance between the poles. Wrong. A larger gap spreads the field out and weakens the effective field between the poles.
• D. Increases in current without the coil. Wrong. Without the coil there is no electromagnet. The wording is flawed, since the current must flow through the coil.

Tip: Remember "TIC": Turns, Iron core, Current. Increasing any of these strengthens an electromagnet. In JAMB, watch for options that say "decrease" or "without", because they are often the traps.