Which of the following are responsible for occurrence of critical or whirling speed of shaft?
1. Eccentric mounting of the rotor
2. Non-uniform distribution of rotor material
3. Bending of shaft due to the weight of the rotor and the shaft itself
4. Environmental effect such as effect of moisture and temperature
Select the correct answer using the code given below.
(a) 1,2,3 and4 (b) 1,2, and 3only
(c) 1,2,and 4 only (d)1 and 3only