Long Answers

Prepared by: learnloophq@gmail.com

Last edited 26 days ago by Learn LoopHQ.

Chapter: 07. Magnetism

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Explain the attractive and directive properties of a magnet.

The attractive property describes a magnet’s ability to pull magnetic substances towards itself. This magnetic force is strongest at the two ends of the magnet, which are called its poles, with very little or no force in the middle. The directive property refers to a magnet’s tendency to align itself in a specific north-south direction when suspended freely. The end pointing towards geographic north is the magnet’s north pole, and the end pointing towards geographic south is its south pole. This consistent alignment makes magnets useful for direction finding.

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Describe how magnetic poles always exist in pairs, even when a magnet is broken.

A fundamental property of magnets is that they always have two poles: a north pole and a south pole. These poles always exist in pairs and cannot be separated from each other. If you break a magnet into two or more pieces, each resulting piece immediately becomes a complete magnet on its own. Every smaller piece will have its own newly formed north and south poles, demonstrating that isolated magnetic monopoles do not exist. This process can theoretically continue indefinitely, with each fragment retaining bipolarity.

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Explain how magnetic fields are represented and describe two key properties of magnetic lines of force.

The magnetic field, which is the region around a magnet where its influence can be felt, is represented by imaginary curved lines known as magnetic lines of force. These lines can be visualized by sprinkling iron filings around a magnet, where they arrange themselves in a distinct pattern. Two key properties of these lines are that they are closed, continuous curves, meaning they always form complete loops, originating from the north pole and ending at the south pole externally. Additionally, magnetic lines of force never intersect each other, as doing so would imply two directions for the magnetic field at a single point, which is physically impossible. They also tend to be denser near the poles, indicating a stronger magnetic field.

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Describe why the Earth acts like a giant magnet and how this affects a compass.

The Earth acts like a huge bar magnet due to the movement of molten iron and nickel in its outer core, generating a vast magnetic field. Importantly, the Earth’s magnetic south pole is located near the geographic north pole, and its magnetic north pole is near the geographic south pole. This magnetic field is why a compass works. When a magnetic compass is used, its small magnetic needle, which acts like a tiny bar magnet, aligns itself with Earth’s magnetic field lines. The north pole of the compass needle is attracted to Earth’s magnetic south pole (near geographic north), causing it to point towards the geographic north, thus demonstrating Earth’s directive influence.

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Explain what an electromagnet is, how its strength can be controlled, and list some of its uses.

An electromagnet is a temporary magnet created by passing an electric current through a coil of wire wound around a soft-iron core. The soft iron core becomes magnetized only as long as the current flows. Its strength can be precisely controlled by two main factors: increasing the number of turns in the coil, and increasing the amount of electric current flowing through the coil. Electromagnets are incredibly versatile and have numerous uses, including in electric bells, telephones, and radios. They are also vital in industrial applications such as cranes for lifting heavy iron and steel loads, and in medical procedures for removing iron bits from wounds.

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Differentiate between permanent and temporary magnets.

Permanent magnets retain their magnetic properties over a long period and have fixed north and south poles. They are typically made from hard magnetic materials like steel, and their strength is generally constant. In contrast, temporary magnets only exhibit magnetic properties temporarily, often when under the influence of another magnet or an electric current. They are usually made from soft magnetic materials like soft iron, and their north and south pole positions can change depending on how they are induced, and their strength can also be varied. Electromagnets, with a soft iron core, are a common type of temporary magnet.

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Describe at least four ways a magnet can be demagnetized.

Demagnetization is the process of destroying a magnet’s magnetic properties. One common way is by heating the magnet to a very high temperature, as the increased thermal energy disrupts the internal alignment of its magnetic domains. Another method is through hammering the magnet repeatedly, which physically disorients its magnetic domains. Similarly, dropping the magnet frequently from a height can also cause it to lose its magnetism over time due to repeated shocks. Finally, passing a strong alternating electric current through or near the magnet can scramble its magnetic orientation, leading to demagnetization. Leaving the poles of magnets bare for a long time can also result in slow self-demagnetisation.

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