Analytical Classics of Junior High School Physics

Author: Wu Shichen
Publisher:
Publication Date: 2001-09-01
Features: The Dictionary of Typical Physics Problems for Junior High School is divided into five parts: Mechanics, Acoustics, Thermodynamics, Optics, and Electricity. It not only helps readers understand the solutions to each problem but also aims to clarify the purpose of solving each problem, as well as its difficulties, ambiguities, and the expected educational benefits and gains.
Chapter: Preliminary Knowledge of Measurement
Physics requires the quantitative study of physical phenomena, so it is necessary to measure relevant physical quantities. Therefore, understanding some preliminary knowledge of measurement and mastering basic measurement skills are essential preparations for studying physics. Many physical quantities can be directly measured using instruments. Different physical quantities require different measuring tools, with corresponding methods and requirements. However, general measurements should adhere to six key principles:
1. Adjusting (): This means knowing how to adjust to zero or level. Before using a tool, ensure that the pointer of a spring scale, ammeter, or voltmeter does not point to "0" and adjust it to the zero mark; if the beam of a balance is not balanced, adjust it first.
2. Identifying (): For each measuring tool, you must first identify its range and the smallest division. When using a ruler, you should also recognize the starting position of the measured object on the scale.
3. Positioning/Connecting (/): The ruler should be placed upright, with its scale aligned closely with the measured object; balances and graduated cylinders should be placed on a horizontal surface; an ammeter should be connected in series with the circuit being measured, while a voltmeter should be connected in parallel.
4. Reading (): The eyes should be aligned perpendicular to the scale to read the measurement accurately.
5. Interpreting (): For a ruler, in addition to reading the accurate value, estimate the next smallest division. At the junior high level, other measuring tools do not need to be estimated to the next smallest division.
6. Recording (): Record measurement data correctly. When using a ruler to measure length, record both the accurate and estimated values, along with the unit. For other measuring tools, only the accurate value and unit need to be written.