A coupling is a device used to connect two shafts together at their ends for the purpose of transmitting power. The primary purpose of couplings is to join two pieces of rotating equipment while permitting some degree of misalignment or end movement or both. 

Addition of small quantity of copper increases resistance to corrosion

Manganese is added to improve strength and hardness of steel . Based on Manganese content, steel are classified as Carbon Manganese steel (Mn >1%) and Carbon Steel (Mn <1%). If its content exceeds 1.5%, it increases the formation of martensite and hence decreases ductility and toughness.

The formula is n = 60 x f /p

Where n = synchronous speed; f = supply frequency & p = pairs of poles per phase.

1000=60*50/P

P=60*50/1000

P=3 Pair of Poles or 6 poles

The motor draws about 5 to 6 times current of its full load current and produce very less torque. The most of the current is reactive in nature and does not contribute in production of torque. That is why the starting torque of the squirrel cage induction motor is low.

The frequency of rotor current fr = s*f

F is the frequency of the supply current

S is the slip of the induction motor

fr = 50 X 4/100 = 2 Hz

The moment of inertia of a solid cone of mass ‘m’ and base radius ‘r’ about its vertical axis is

Iz = 3mr²/10

As tensile test performed on a mild steel which is a ductile material, the length of material increases and due to increasing the length, diameter of rod decreases.

For ductile material, tensile and compression are almost the same. For Brittle material, strength in compression is more than tensile. So, the compression test is performed for brittle material.

The slenderness ratio is defined as the ratio of length l to the radius of gyration k, represented as l/k.It is used to find out whether a column is long, intermediate or short.