10 - Science - 14. Physics - Measuring Instruments

Explanation
A screw gauge is a highly precise instrument used to measure the dimensions of very small objects. It consists of a screw mechanism that allows for extremely accurate measurements. The answer of 0.01 mm indicates that the screw gauge can measure objects with a precision of one hundredth of a millimeter. This level of accuracy is necessary when dealing with very small objects, such as microchips or microscopic organisms, where even the smallest variations in dimension can have significant effects.

Explanation
The given question is asking about the zero error in a screw gauge where the zero of the head scale lies below the pitch scale axis. In this case, the zero error is positive. This means that the actual measurement will be greater than the reading obtained from the instrument.

Explanation
A screw gauge is used to measure the diameter of a thin wire because it provides a more precise measurement than other measuring instruments. The screw gauge consists of a screw mechanism that moves a spindle towards or away from an anvil. By rotating the thimble, the spindle moves, allowing for accurate measurements of the wire's diameter. This is particularly useful for measuring thin wires, as their small size requires a high level of precision.

Explanation
One astronomical unit is the distance between the center of the earth and the center of the Sun. This unit is used to measure distances within our solar system. The center of the Moon and the center of Mars are not used as reference points for measuring astronomical units.