The component with the greatest resistance dissipates the most power in a series circuit. In a series circuit, the same amount of current flows through all resistors, and power is the product of the square of the current and resistance, I2R.
In a parallel circuit, the component with the least resistance dissipates the most power in a parallel circuit, as the voltage across resistors remains the same, and power is the product of voltage and current (V×I). Read more