1. According to Ohm's Law

Ohm's Law Formula

When the resistance (R) is constant, according to Ohm's Law (I = U/R), it can be rearranged as U = IR. Therefore, if you know the change in current (I) and the value of resistance (R), you can find the voltage (U) using this formula. For example, given a resistance R = 5Ω, and the current changes from 1A to 2A, when the current I = 1A, the voltage U1 = IR = 1A × 5Ω = 5V; when the current I = 2A, the voltage U2 = 2A × 5Ω = 10V.

Experimental Exploration Situation

In the experiment exploring the "relationship between current and voltage," the current is changed by varying the resistance of the slider pot connected to the circuit, while simultaneously measuring the corresponding voltage values. If you have data on how the current changes over time or with other variables, and you know the resistance value in the circuit (e.g., the resistance of a fixed resistor), you can use U=IR to calculate the corresponding voltage values. Moreover, in such experiments, it is often the case that different voltage values are set first, the corresponding currents are measured, and then an  I−U graph can be plotted based on the measurement results. If, on the contrary, the change in current is known, the voltage value can also be obtained using the slope of this graph (the slope is equal to 1/ $\frac{\mathrm{<span\; style="font-family:\; arial,\; helvetica,\; sans-serif;\; font-size:\; 16px;">R)\; and\; the\; current\; value.\; For\; example,\; if\; the\; current\; at\; a\; certain\; moment\; is </span>}}{}$ $\mathrm{<br>}$I from the graph, and the resistance R $$=k1 ( $\mathrm{<br>}$k is the slope of the graph), then the voltage  $\mathrm{<br>}$U=IR.

II. Analyzing in the Circuit

Series Circuit

In a series circuit, the source voltage Utotal is equal to the sum of the voltages across each part, i.e.,  ${\mathrm{<br>}}_{}$Utotal=U1+U2+⋯+Un. If you know the voltage variations of other components (excluding the component corresponding to the voltage being studied) in the circuit and the source voltage, you can find the voltage of the desired component. For example, in a series circuit with resistors  ${\mathrm{<br>}}_{}$R1 andR2, and a source voltage Utotal=10V, if the voltage U1 across  ${\mathrm{<br>}}_{}$R1 changes from  $\mathrm{<br>}$3V to  $\mathrm{<span\; style="font-family:\; arial,\; helvetica,\; sans-serif;\; font-size:\; 16px;">4V with\; the\; change\; in\; current,\; according\; to </span>}$ ${\mathrm{<br>}}_{}$U2=Utotal−U1, when U1=3V, $$  
U2=10V−3V=7V; whenU1=4V,  ${\mathrm{<br>}}_{}$U2=10V−4V=6V.

Parallel Circuit

In a parallel circuit, the voltage at both ends of each branch is equal and equal to the power supply voltage, i.e.,U=U1=U2=⋯=Un. If the power supply voltage or the voltage of a certain branch is known, then regardless of how the current changes, the voltages of other branches are equal to this value. For example, in a parallel circuit with a power supply voltage of  $\mathrm{<br>}$6V, no matter how the current in the branches changes, the voltage across each branch remains  $\mathrm{<br>}$6V.