Refer to figures.
An increase in total rotor thrust requires an increase in the total reaction, which in turn will increase total drag. Engine power must, therefore, be increased to maintain N_R when increasing total rotor thrust, and vice versa.

Rotor thrust will cause the blades to rise, until they reach a position where their upward movement is balanced by the centrifugal force produced by the blades’ rotation.

When raised like this, the blades are said to be coned upwards. The coning angle is measured between the span-wise length of the blade and the tip path plane and will vary with combinations of rotor thrust and N_R.

If rotor thrust is increased and N_R remains constant, the blades will cone up. If N_R is reduced, centrifugal force reduces and if rotor thrust remains constant, the blades will cone up as well.

As coning angle increases, the blade thrust inclines more to the centre, so the total rotor thrust decreases. Accordingly, a bigger pitch angle is required to provide the same total rotor thrust.