📚 Variables in AQA A-Level Physics | AQA A-Level 物理中的变量
In AQA A-Level Physics, variables are the quantities you change, measure or keep the same during an experiment. Identifying them correctly is essential for planning practicals, collecting valid data and answering exam questions accurately.
在 AQA A-Level 物理中，变量是你在实验中改变、测量或保持不变的量。正确识别变量对于规划实验、收集有效数据以及准确回答考试问题至关重要。
1. What is a Variable? | 什么是变量？
In AQA A-Level Physics, a variable is any quantity that can change or be changed during an investigation. Variables may be physical quantities such as length, current, temperature, time or force. Correct identification of variables is the first step in designing a valid experiment.
在 AQA A-Level 物理中，变量是在实验中可以改变或发生变化的任何量。变量可以是长度、电流、温度、时间或力等物理量。正确识别变量是设计有效实验的第一步。
The three main types of variable are the independent variable, the dependent variable and control variables. You must be able to identify each one from a method or a description of an experiment, as this is regularly tested in AQA practical questions.
三种主要变量类型是自变量、因变量和控制变量。你必须能够从实验方法或实验描述中识别每一种变量，这是 AQA 实验题中经常考查的内容。
2. Independent Variable (IV) | 自变量
The independent variable is the quantity you deliberately change or select in an experiment. It is the input variable and is plotted on the x-axis of a graph. In an experiment to investigate how the current through a resistor depends on potential difference, the potential difference is the independent variable because you set it using a power supply.
自变量是你在实验中故意改变或选择的量。它是输入变量，绘制在图形的 x 轴上。在探究通过电阻的电流如何取决于电势差的实验中，电势差是自变量，因为你使用电源设定它。
In some investigations the independent variable is not a continuous quantity but a categoric one, such as the type of material or the colour of light. You still record it in the first column of a results table and use it to label the x-axis.
在某些探究中，自变量不是连续量，而是分类量，例如材料类型或光的颜色。你仍然将其记录在结果表的第一列中，并用它标注 x 轴。
3. Dependent Variable (DV) | 因变量
The dependent variable is the quantity you measure for each value of the independent variable. It is the output variable and is plotted on the y-axis. You do not set it directly; it changes as a result of the independent variable.
因变量是你针对每个自变量值测量的量。它是输出变量，绘制在图形的 y 轴上。你不直接设定它，它因自变量的改变而变化。
For example, when measuring the extension of a spring loaded with different masses, the extension is the dependent variable because it depends on the force applied by the masses. In this case the force is the independent variable.
例如，在测量弹簧在不同质量负载下的伸长量时，伸长量是因变量，因为它取决于质量施加的力。在这种情况下，力是自变量。
4. Control Variables | 控制变量
Control variables are quantities that could affect the dependent variable but must be kept constant throughout the experiment. Keeping them constant ensures that any change in the dependent variable is caused only by the independent variable. This is called a fair test.
控制变量是可能影响因变量但在整个实验过程中必须保持不变的量。保持它们不变可确保因变量的任何变化仅由自变量引起。这称为公平测试。
Common control variables include temperature, pressure, material, cross-sectional area, length of wire, and the initial conditions of the apparatus. For example, in a resistance experiment, the temperature of the wire must be controlled because resistance increases with temperature.
常见的控制变量包括温度、压力、材料、横截面积、导线长度以及设备的初始条件。例如，在电阻实验中，必须控制导线的温度，因为电阻随温度升高而增大。
5. Categoric, Continuous and Discrete Variables | 分类变量、连续变量和离散变量
AQA requires you to recognise three types of variable or data. A categoric variable has labels or names rather than numerical values, such as type of metal or type of surface. A continuous variable can take any value on a scale, such
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