Ohm's law actually discusses the relationship between current and voltage, current and resistance, not the relationship between voltage and current, nor the relationship between resistance and current.

In the formula of ohm's law, current is the ratio of voltage to resistance. When the voltage and current change, the resistance of the conductor remains the same, that is to say, the resistance of the conductor is a property of the conductor and has nothing to do with the voltage and current. Many students easily analyze the formula of ohm's law from the mathematical point of view, and think that the understanding that resistance is directly proportional to voltage and inversely proportional to current is actually wrong.

For the study of ohm's law, in addition to the application of knowledge points and formulas involved in textbooks, we should also know that ohm's law is only applicable to pure resistance circuits. For example, our common fixed values, resistors, sliding rheostats, and the resistance of small bulbs are all pure resistance appliances. In addition, household appliances such as rice cookers and electric irons are also pure resistance appliances.

In addition to understanding the relationship between ohm's law, ohm's law should be applied, so that the characteristics of resistors in different circuits can be smoother in the process of analyzing circuits. In a series circuit, the total resistance of the circuit is equal to the sum of the resistances of each resistor. In parallel circuit, the calculation method of total resistance in the circuit is different.