Science (086) — CBSE Class 10 board question

(B) direction of the current flowing through it

The strength (magnitude) of the magnetic field of a solenoid depends on the number of turns, current magnitude, and core material — but NOT on the direction of current, which only affects the polarity, not the strength.

• The question tests the difference between strength (magnitude) and direction of the magnetic field.
• Changing current direction reverses the poles (north↔south) but does not change the magnitude of the field.
• Number of turns, current magnitude, and core material (e.g., soft iron core increases field strength) all affect the strength.
• Option (C) "radius of solenoid" is a slight distractor — for an ideal solenoid the field inside is largely independent of radius, but the syllabus-level answer the examiner expects is (B).