Formula
The current in a part of a circuit is directly proportional to the voltage and inversely proportional to the resistance.
ENT-level problem
A resistor of resistance $R = 10$ ohm is connected to a source of voltage $U = 20$ V. Find the current flowing through the resistor.
Ohm's law for a circuit segment: $I = U/R$.
$$I = \frac{U}{R} = \frac{20}{10} = 2 \text{ A}$$
Ohm's law for a part of a circuit links three quantities: voltage U, current I and resistance R. Given any two, the third follows from the formula — the calculator above does it automatically and shows the steps.
The law applies to an ohmic segment: if the resistance depends on the voltage (a filament lamp, a diode), this form of Ohm's law does not hold.
Multiply the current by the resistance: U = I · R. For I = 5 A and R = 40 Ω the voltage is 200 V.
The current in a part of a circuit is directly proportional to the voltage and inversely proportional to the resistance: I = U / R.
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