2013 SEC 4 Physics Test - Magnetism

When two like poles of magnets are brought near to each other, they will experience repulsion. This is because like poles of magnets have the same magnetic polarity, which causes them to repel each other. This repulsive force is a fundamental property of magnets and is a result of the alignment of magnetic domains within the magnets.

The process that enables the nails to attract one another is called induction. Induction occurs when an object becomes electrically charged without direct contact with a charged object. In this case, the nails are attracting each other due to the presence of an electric charge induced in them.

Option D correctly shows the arrangement of the magnet. In this arrangement, the plotting compasses are pointing towards the North Pole of the bar magnet. This indicates that the North Pole of the magnet is located towards the top of the paper, while the South Pole is located towards the bottom.

Using alternative current is the correct answer because when an alternating current is passed through a magnet, it creates a continuously changing magnetic field. This changing magnetic field disrupts the alignment of the magnetic domains within the magnet, causing it to lose its magnetism or become demagnetized.

Magnets always have opposite polarities, meaning that one end is a north pole and the other end is a south pole. This is a fundamental property of magnets and is necessary for their attraction and repulsion. Therefore, the statement "They may not have opposite polarities" is not a property of magnets and is incorrect.

The most appropriate method to show that a substance is a magnet is if it can repel another magnet. This is because magnets have two poles, a north pole and a south pole, and like poles repel each other. If a substance can repel another magnet, it indicates that it also has magnetic properties and is therefore a magnet itself.

A permanent magnet is not used in a circuit breaker. Circuit breakers are designed to interrupt the flow of electric current in a circuit when there is an overload or a fault. They typically use electromagnets or solenoids to detect the abnormal current and trip the breaker. Permanent magnets, on the other hand, are commonly used in generators, electric motors, and loudspeakers to create magnetic fields for various purposes.

Steel is the most suitable material to be made into a permanent magnet because it has a high magnetic permeability, which allows it to retain its magnetism for a longer period of time. Steel also has a high coercivity, meaning it requires a large amount of magnetic force to demagnetize it. This makes steel an ideal choice for creating magnets that can be used in various applications, such as motors, generators, and magnetic storage devices.

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Steel is the most suitable substance to be used as the needle of a plotting compass because it is a magnetic material. Steel contains iron, which is highly magnetic, making it ideal for creating a compass needle that can align with the Earth's magnetic field. Copper, iron, and aluminium are not as magnetic as steel, so they would not be as effective in accurately pointing towards magnetic north.