What is tractive effort in electric traction?

• The energy consumed per km

• The force exerted by the train on the track

• The force exerted by the motor on the wheels to move the train

• The braking force applied during retardation

Answer explanation

Tractive effort refers to the force exerted by the motor on the wheels to move the train. This force is crucial for overcoming resistance and enabling acceleration, making it the correct choice among the options provided.

The tractive effort (F) required to accelerate a train is directly proportional to:

• Train weight

• Final speed

• Acceleration

• Both A and C

Answer explanation

The tractive effort (F) is directly proportional to both the train weight (A) and the acceleration (C). Therefore, the correct answer is 'Both A and C', as both factors influence the force needed to accelerate the train.

Which factor does NOT affect specific energy consumption?

• Train load

• Track gradient

• Number of passengers

• Type of train windows

Answer explanation

The type of train windows does not influence specific energy consumption. In contrast, train load, track gradient, and number of passengers directly impact energy usage during operation.

What is the unit of specific energy consumption?

• Newton

• Joule

• kWh/ton-km

• Watt/km

Answer explanation

Specific energy consumption measures energy used per unit of transport, typically expressed as kWh/ton-km. This indicates how much energy is consumed to transport one ton of goods over one kilometer.

If a train of mass 300 tons accelerates at 0.5 m/s², what is the tractive effort?

• 1500 N

• 15000 N

• 150000 N

• 1.5 MN

Answer explanation

To find the tractive effort, use the formula: Force = mass × acceleration. Convert 300 tons to kg (300,000 kg) and calculate: 300,000 kg × 0.5 m/s² = 150,000 N or 1.5 MN. Thus, the correct answer is 1.5 MN.

The coefficient of adhesion is defined as:

• Ratio of tractive effort to total weight

• Ratio of adhesive weight to tractive effort

• Ratio of tractive effort to adhesive weight

• Ratio of adhesive weight to total train weight

Answer explanation

The coefficient of adhesion is defined as the ratio of tractive effort to adhesive weight. This measures how effectively a vehicle can utilize its weight to generate traction, making the correct choice: Ratio of tractive effort to adhesive weight.

If the adhesive weight is 50 tons and the coefficient of adhesion is 0.2, what is the maximum tractive effort without slipping?

• 10,000 N

• 100,000 N

• 50,000 N

• 200,000 N

Answer explanation

The maximum tractive effort can be calculated using the formula: Tractive Effort = Adhesive Weight × Coefficient of Adhesion. Here, 50 tons (50,000 kg) × 0.2 = 10,000 kgf, which converts to 100,000 N. Thus, the correct answer is 100,000 N.

The effect of increasing braking retardation is:

• Reduces travel time

• Increases mechanical stress

• Improves energy efficiency

• All of the above

Answer explanation

Increasing braking retardation reduces travel time by stopping quicker, increases mechanical stress on components due to higher forces, and can improve energy efficiency by converting kinetic energy into heat more effectively. Thus, the correct answer is 'All of the above'.

Which of the following will increase specific energy consumption?

• Reduced acceleration

• Smooth track

• Steep gradients

• Lower speed

Answer explanation

Steep gradients increase the energy required to move against gravity, leading to higher specific energy consumption. In contrast, reduced acceleration, smooth tracks, and lower speeds generally decrease energy use.

A train consumes 300 kWh of energy over a run of 10 km, carrying 200 tons. What is the specific energy consumption?

• 0.15 kWh/ton-km

• 1.5 kWh/ton-km

• 0.03 kWh/ton-km

• 3 kWh/ton-km

Answer explanation

To find specific energy consumption, divide total energy by the product of distance and weight: 300 kWh / (10 km * 200 tons) = 0.15 kWh/ton-km. Thus, the correct answer is 0.15 kWh/ton-km.