जब एक अचुम्बकीय पदार्थ को एक शक्तिशाली चुम्बक के पास लाया जाता है वह प्रतिकर्षित हो जाता है , पदार्थ है -

Explanation

Since iron is a magnetic material, its atoms have permanent magnetic dipole moment. But normally these are randomly oriented so that there is no net magnetization. In the presence of another magnet these atomic dipoles are aligned with one another to generate spontaneous temporary magnetic moment in the iron block. Due to this spontaneous magnetization, iron block (which is not magnetised) is attracted towards the magnet. Always remember that both objects must have net magnetic moments to generate magnetic force on each other. As the magnetic dipole moment is generated in the iron block, then only the magnetic force between the two comes into play. In absence of the magnet, these aligned atomic dipoles are disturbed again due to thermal energy and the block loses the magnetism acquired spontaneously on the approach of the magnet.