Simple phenomena of magnetism：練習題

Which material is commonly used to make a temporary magnet?

A student uses a plotting compass to map the magnetic field lines around a bar magnet. At a certain point P, the needle of the compass points towards the South pole of the magnet.

Which statement correctly describes the magnetic field direction and the force experienced by a North pole placed at point P?

A sensitive plotting compass is placed at a point near a thick steel bar that has been placed inside a solenoid through which a large direct current (d.c.) is passing. The current is then switched off and the bar is removed. The plotting compass is then used to investigate the region around the steel bar.

Which statement best explains the observations made and the property of the material used?

A student has two metal bars that look identical. Which of the following is the only certain test to confirm that both bars are permanent magnets?

A student has two identical-looking rods, X and Y. One is a permanent magnet and the other is a soft iron rod. The student places rod Y on a table and brings rod X vertically down towards the center of rod Y as shown in a T-shape configuration. It is found that there is no magnetic force between the rods.

Which conclusion must be correct?

State the direction of a magnetic field at any point in space in terms of the force acting on a specific magnetic pole.

A student uses a plotting compass to map the magnetic field lines around a bar magnet. Explain how the student can determine where the magnetic field is strongest by observing the pattern of these field lines.

An electron enters a uniform magnetic field at a right angle to the field lines. Describe the direction of the force acting on the electron relative to its velocity and the magnetic field, and state which rule is used to determine this.

A student uses a permanent bar magnet to investigate induced magnetism in a bar of soft iron.

(a) Describe what happens to the internal magnetic arrangement of the soft iron bar when the permanent magnet is brought close to one end. (2)
(b) State why steel is a better choice than soft iron for making a permanent magnet, referring to its ability to retain magnetism. (1)