Magnetic Compass Needle Bearing

The needle of a magnetic compass is generally supported on a jewel bearing. The magnetic compass is a navigation instrument that uses the Earth's magnetic field to determine the direction of north. The needle of the compass is magnetized and is supported on a bearing that allows it to rotate freely. There are several types of bearings that are used to support the needle of a magnetic compass, including bush bearings, ball bearings, needle bearings, and jewel bearings.

Jewel Bearings

Jewel bearings are the most commonly used type of bearing in magnetic compasses. They are made of a hard, smooth material, such as sapphire, ruby, or diamond, and are used to reduce friction and wear on the needle. The jewel bearings are usually mounted in a brass or steel cup that is attached to the compass housing. The needle is then mounted on the jewel bearings and is able to rotate freely.

Advantages of Jewel Bearings

There are several advantages to using jewel bearings in magnetic compasses:

1. Low Friction: Jewel bearings have a very low coefficient of friction, which means that they offer very little resistance to the movement of the needle. This allows the needle to rotate freely and respond quickly to changes in the Earth's magnetic field.

2. High Precision: Jewel bearings are very precise and accurate, which is important for navigation purposes. They are able to maintain their shape and size over time, which ensures that the needle remains stable and consistent.

3. Longevity: Jewel bearings are very durable and can last for many years without needing to be replaced. They are able to withstand high temperatures and pressures, as well as exposure to dust, dirt, and other contaminants.

Conclusion

In conclusion, the needle of a magnetic compass is generally supported on a jewel bearing. Jewel bearings offer low friction, high precision, and longevity, which are important characteristics for a navigation instrument. By using a jewel bearing, the magnetic compass is able to provide accurate and reliable information about direction and orientation.