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
Ft = Tractive effort
W = Adhesive Weight
Galvanized steel conductors do not corrode, and possess high resistance. Hence such Wires are used in telecommunications circuits, earth wires, guard wire, stray wire, etc.
In two wattmeter method the phase angle is tanφ = √3(W1 − W2)/(W1 + W2) tanφ = √3(500 − 500)/(500 + 500) tanφ = 0° φ = tan−10° = 0° Power factor = cosφ PF = cos0° = 1
Voltage V = 230 V
Current I = 2 A
Resistance R = V/I
R = 230/2 = 115 Ω
In DC series motor Torque (Ta) increase as the Square of armature current (Ia) Ta ∝ Ia2. So DC motor provides high starting torque.