Regard as a positively charged particle in a circuit. As it moves during a resistor in the circuit the positively charged particle moves from a point one end of the resistor in the circuit where the electric potential is high to a point the other end of the resistor where the electric potential is low. That signifies it moves from a point where it has high potential energy to a point where it has low potential energy. Conservation of energy would propose that the decrease in the potential energy of the particle should be accompanied by an increase in kinetic energy. Why doesn't the particle speed up as it goes through the resistor?

Answer:

Inside a resistor the electric potential energy is converted to thermal energy.