CBSE Class 12 · 2009 · Magnetic Effects of CurrentVery Short Answer

Magnetic field lines can be entirely confined within the core of a toroid, but not within a straight solenoid. Why?

Answer: Because a toroid has no ends, whereas a solenoid does.

Solution

For a straight solenoid the field lines must emerge from its two ends to form closed loops in the surrounding space, since the net magnetic flux through any closed surface is zero. A toroid is a closed ring with no ends, so its field lines close on themselves entirely within the core.

CBSE Class 12 Board · 2009 · Subjective

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