D68 FACE THE CHALLENGE

If the head of water is 30 m and the efficiency of the turbine is 85%, what is the output power for a discharge of 5 m³/s? (Take g = 9.81 m/s²)

• 1.25 MW
• 1.15 MW
• 1.35 MW
• 1.05 MW

Answer explanation

P = η * ρ * g * Q * H = 0.85 * 1000 * 9.81 * 5 * 30 = 1.25 MW

Assertion (A): Pelton wheel is suitable for low head and high discharge. Reason (R): It operates on the principle of impulse of water.

• A is true, R is true and R is the correct explanation of A
• A is true, R is true but R is not the correct explanation of A
• A is true, R is false
• A is false, R is true

Answer explanation

Pelton wheels are impulse turbines suitable for high heads and low discharge

In hydroelectric projects, surge tanks are provided to:

• Prevent water hammer
• Increase efficiency
• Store water
• Control silt entry

Answer explanation

Surge tanks absorb sudden changes in water flow and reduce water hammer.

Which type of dam is most suitable for narrow valleys?

• Arch dam
• Gravity dam
• Embankment dam
• Buttress dam

Answer explanation

Arch dams are best suited for narrow valleys with strong abutments.

The standard penetration test (SPT) is used to determine:

• Bearing capacity of soil
• Water content
• Permeability
• Shrinkage limit

Answer explanation

SPT measures soil resistance to penetration, indicating bearing capacity.

In RCC, minimum grade of concrete for severe exposure condition is:

• M20
• M25
• M30
• M35

Answer explanation

IS 456 specifies M30 as minimum for severe exposure.

The primary function of a draft tube in a reaction turbine is to:

• Recover kinetic energy
• Increase head
• Reduce cavitation
• All of the above

Answer explanation

Draft tube recovers kinetic energy and reduces velocity losses.

In surveying, the method suitable for locating inaccessible points is:

• Resection

• Radiation
• Traversing
• Intersection

Answer explanation

Intersection uses measured angles from two points to locate an inaccessible point.

In RCC beams, side face reinforcement is provided when depth exceeds:

• 800 mm

• 750 mm

• 1000 mm
• 1200 mm

Answer explanation

Side face reinforcement is required for deep beams with depth > 750 mm.

The most efficient cross-section for a channel is one which:

• Has least wetted perimeter
• Has maximum wetted perimeter
• Has rectangular shape
• Has trapezoidal shape

Answer explanation

Efficiency is achieved with least wetted perimeter for given area.