Olympiad Test: Fun with Magnets - Class 6 MCQ

A magnet is an object that attracts things made up of iron, steel, nickel and cobalt. In containers (i) and (ii), iron nail and steel nail are magnetic materials whereas copper coin and aluminium earring are non-magnetic materials. In container (iii), both marble and gold coin are non-magnetic materials and in container (iv), both nickel coin and steel nail are magnetic materials. So, Reeta can use a magnet to separate the objects only in containers (i) and (ii).

Every magnet has two poles, whatever the shape may be. These poles are near the free ends of a magnet. One end of a magnet is called the North Pole and the other end is called the South Pole. They are represented as N for North Pole and S for the South Pole. The force of attraction or repulsion in a magnet is strongest at the poles. Here, P and S are the poles of the magnet and the magnetic force is strongest at these ends. So, they will attract the maximum number of pins.

Magnetization is the vector field in classical electromagnetism that expresses the density of permanent or induced magnetic dipole moments in a magnetic substance. The direction of movement within this area is classified as either Axial or Diametric. The magnetic moments that cause magnetization can be caused by small electric currents caused by electron mobility in atoms, or by the spin of the electrons or nuclei. The response of a substance to an external magnetic field produces net magnetization.
Procedure:

• The steel bar is stroked in one direction from one end to the other with the same pole of the permanent magnet.
• Between strokes, the stroking magnet must be elevated sufficiently enough above the steel bar.
• Because the atomic magnets in the domain are attracted to the stroking pole, the steel bar will become a magnet with a pole formed at the end where the strokes cease, which is opposed to the stroking pole.
• When employing two magnets, the stroking poles of each magnet must be opposed, and the steel bar must be stroked in the opposite way.
• Stoking with two magnets is faster than with one magnet.
• The striking approach creates only weak magnets.
• As a result, Q becomes the North pole, and R becomes the South pole, where the rubbing magnet is raised.

Hence option B is correct.

We know that the substances that are attracted by the magnet are called magnetic substances. Here, it is given that when the bar magnet moves, it is able to drag the match box along. Hence, the match box must contain a steel ball bearing in it, as it is attracted by the magnet. Marble, toothpick and copper coin may not get attracted to the magnet.

A freely suspended magnet always rests pointing in the North-South direction. The end of the magnet that points towards North is called its North-seeking end or the north pole of the magnet. The other end that points towards the South is called the South-seeking end or the south pole of the magnet. Like poles always repel each other while unlike poles always attract each other. Here the like poles of both magnets are in contact with each other. Thus, if the force on magnet P is removed, the magnet P will repel magnet Q.

Three magnets, A, Y, and Z, were dipped in a heap of iron filling. The figure shows the amount of iron filing sticking to them. The strength of these magnets will be X > Y > Z.
As we know, the stronger the magnet, the greater will be the iron filing sticking on them. More iron filings stick in the magnet because the magnetic strength of a bar magnet will be maximum at its ends. So from the figure, it is clear that the iron filings stuck on X are the most and Z are the least. So the strength of the bar magnets will be in the order X > Y > Z.

The unlike poles were facing each other causing the two magnets to be attracted to each other. As magnet P moved towards magnet Q, the spring coil extended.

Wood placed across the poles will preserve the magnetism for a long time.

Magnetic force is not only a pulling force; it can also be a pushing force. Like poles of a magnet repel each other, and opposite poles attract. So, the statement "Magnetic force is a pulling force only" is incorrect.

• A is correct because increasing the number of strokes while creating magnets can strengthen the magnetic field.
• B is correct because increasing the number of coils around a nail increases the strength of the magnetic field (as in the case of an electromagnet).
• D is correct because heating a magnet to a very high temperature can cause it to lose its magnetic properties.

• Magnetic substances are substances that get attracted to magnets. Few of the magnetic substances are - iron, steel, cobalt and nickel.
• Non-magnetic substances are substances that do not get attracted by a magnet. Few of the materials are wood, plastic, copper, rubber, brass.