Magnetism and Electromagnetism
A certain amount of current flows through a ring shaped coil with fixed number of turns. How does the magnetic induction B varies inside the coil if an iron core is threaded into coil without dimensional change of coil?

Increases
Remains same
First increases and then decreases depending on the depth of iron in¬sertion
Decreases

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Magnetism and Electromagnetism
A permanent magnet

Attracts ferromagnetic substances and repels all others
Attracts some substances and repels others
Attracts only ferromagnetic substances
Attracts all paramagnetic substances and repels others

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