Topic: Fluid Mechanics
A pump running at 1000 rpm consumes 1 kW and generates head of 10m of water. When it is operated at 2000rpm, its power consumption and head generated would be
- A. 4 kW, 50m of water
- B. 6 kW, 20m of water
- C. 3 kW, 30m of water
- D. 8 kW, 40m of water
Answer: D. 8 kW, 40m of water
Explanation: Using pump affinity laws, the head is proportional to the square of the speed ($H \propto N²$), and power is proportional to the cube of the speed ($P \propto N³$). The speed ratio is $N_2/N_1 = 2000/1000 = 2$. Therefore, the new head is $H_2 = 10 \times 2^2 = 40$ m. The new power consumption is $P_2 = 1 \times 2^3 = 8$ kW.