Question

Which of the following is not true about the advantages of electromagnet over permanent magnet?

• A. Small electromagnets are used in electronic lock
• B. Scrapyard cranes have powerful electromagnets that lift metal car bodies with ease.
• C. Magnetic Resonance Imaging machines use very powerful electromagnets to produce highly detailed images of the human body.
• D. None of the above

Answer 1

The correct option is D None of the above

Magnets come in two main types: permanent magnets and electromagnets. As its name suggests, a permanent magnet is always magnetized -- think of a kitchen magnet that stays stuck to a refrigerator door for years. An electromagnet is different; its magnetism works only when powered by electricity. Although an electromagnet is more complicated than a permanent magnet, it has useful and important advantages. An electromagnet can be made very strong by increasing the number of turns in the coil, and by increasing the current passing through the coil. On the other hand, a permanent magnet cannot be made so strong.