Magnetism：练习题

Which statement correctly describes the direction of magnetic field lines outside a bar magnet?

A student wants to build a simple electromagnet. Which material should they use for the core to ensure the electromagnet can be switched on and off effectively?

A piece of unmagnetised soft iron is brought near the South pole of a strong permanent magnet. Which statement correctly describes the induced magnetism in the soft iron?

What occurs when the North pole of a permanent bar magnet is brought close to the North pole of another permanent bar magnet?

The diagram shows the magnetic field lines around a bar magnet. At which labeled point is the magnetic field strength the greatest?

Describe the experimental procedure for using a plotting compass to map the magnetic field pattern around a single bar magnet.

A student is investigating the properties of different magnetic materials and the fields they produce.

(a) Explain why steel is classified as a magnetically hard material and why this makes it suitable for use as a permanent magnet.

(b) Two bar magnets are placed on a desk. Describe the force observed when the North pole of one magnet is brought close to the North pole of the second magnet.

(c) Describe a practical procedure using iron filings to reveal the shape of the magnetic field pattern around a bar magnet.

(d) State one safety precaution the student should take when performing the experiment with iron filings.