The average value of the sine wave over one complete cycle is actually zero. Hence, for a sine wave, the average value is defined over half the period. The average value expressed in terms of peak value is given by Average value = 0.637 × peak value
As you can see from the below figure in load Z1 is connected with the only current coil. In Load Z2 both current from the current coil (CC) and voltage from voltage coil (PC) are present (Power = V × I). Hence the Wattmeter will read power consumed by Z2.
When two solid surfaces are brought into contact, a finite normal force is needed to pull the two solids apart. This force is known as the force of adhesion or simply adhesion. The coefficient of adhesion () defined as the ratio of tractive effort required to propel the wheel of a locomotive to its adhesive weight. Adhesion traction is the friction between the drive wheels and the steel rail. µ = Ft/W Where Ft = Tractive effort W = Adhesive Weight