In Ohm`s law, the relationship between voltage, current, and resistance is given by the equation V = IR, where V is the voltage across a resistor, I is the current flowing through the resistor, and R is the resistance of the resistor. According to this law, the voltage across a resistor is directly proportional to the current flowing through it, when the resistance remains constant.

Option 1: A wire bound resistor follows Ohm`s law because it is a passive component that exhibits a linear relationship between voltage and current.

Option 2: A potentiometer is a variable resistance device used to measure and adjust voltage levels. Although its resistance can be varied, it still follows Ohm`s law as long as the resistance value remains constant.

Option 3: The correct answer identifies a junction diode. A junction diode is a semiconductor device that has a nonlinear current-voltage characteristic. It does not obey Ohm`s law, as the relationship between voltage and current is not proportional.

Option 4: An electric bulb, although it has a filament with resistance, does follow Ohm`s law as long as the filament remains at a constant temperature.

Therefore, option 3 (Junction diode) is the correct answer as it does not obey Ohm`s