Science — CBSE Class 10 board question

Electromagnetic Induction: The phenomenon of producing an induced electric current in a coil (or conductor) due to a changing magnetic field (or relative motion between a coil and a magnet) is called electromagnetic induction.

Observation: When a strong bar magnet is held stationary near one end of a coil, the galvanometer shows no deflection.

Justification: Electromagnetic induction occurs only when there is a change in the magnetic flux linked with the coil. When the magnet is stationary, the magnetic flux through the coil remains constant — it does not change with time. Since there is no change in flux, no EMF is induced in the coil, no current flows, and hence the galvanometer needle remains at zero.

Source: Chapter 13 — Magnetic Effects of Electric Current (Electromagnetic Induction section)

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• Examiners expect the definition clearly stated (1 mark), the correct observation — no deflection — stated explicitly (1 mark), and a reason based on the concept of changing flux (2 marks).
• A common mistake is writing "the galvanometer deflects" — remember, only a moving or changing magnet induces current. Stationary magnet = no change in flux = no induced current.
• The key phrase to use: "no change in magnetic flux."