What determines the polarity at the ends of an electromagnet? The

Analyze the question: An electromagnet is a coil of wire (usually wrapped around a soft iron core) that becomes a magnet when current flows. The question asks what decides which end is the North pole and which is the South pole.

Explain the concept: The polarity of an electromagnet depends on the direction of the current in the coil. You can find it with the Right-Hand Grip Rule:

• Grip the coil with your right hand so your fingers curl in the direction of the current.
• Your thumb points toward the North pole.

Another way to check is to look at the end of the coil:

• Current flowing anticlockwise gives a North pole.
• Current flowing clockwise gives a South pole.

Step-by-step evaluation of the options:

• A. Magnitude of the current: This affects the strength of the magnetic field, not which end is N or S. Wrong.
• B. Material of the core: A soft iron core makes the magnet stronger because it concentrates the field. It does not set the polarity. Wrong.
• C. Material of the coil: This affects resistance and current flow, not polarity. Wrong.
• D. Direction of current in the wire: If you reverse the current, the poles swap. This is correct.

Answer: D. direction of current in the wire

Exam tip: Remember the split:

• Strength depends on the number of turns, the size of the current, and the core material.
• Polarity depends on the direction of the current.

When you see "polarity" or "which end is North" in an electromagnetism question, think "direction of current".