Explanation:

Introduction:
V-belts are a type of power transmission belt that have a trapezoidal or V-shaped cross-section. They are commonly used for transmitting power between two rotating shafts in industrial applications.

Explanation:
The correct answer is option B, "No, trapezium." V-belts have a trapezoidal or V-shaped cross-section, which allows them to fit securely into the grooves of pulleys. This shape ensures a better grip and reduces the likelihood of slippage, making V-belts an efficient means of power transmission.

Characteristics of V-belts:

1. Trapezoidal Cross-Section: V-belts have a trapezoidal cross-section, with the top surface being wider than the bottom surface. This shape allows for better contact with the pulley grooves, increasing the frictional grip and preventing the belt from slipping.

2. Reinforced Construction: V-belts are typically made of a reinforced rubber material. The reinforcement can be in the form of fabric layers or cords, such as polyester or aramid fibers, embedded within the rubber. This enhances the strength and durability of the belt.

3. Flexibility: V-belts are designed to be flexible, allowing them to bend and wrap around pulleys of varying diameters. This flexibility enables smooth power transmission and reduces the stress on the belt and pulley system.

4. High Power Transmission Capacity: V-belts are capable of transmitting high amounts of power due to their trapezoidal shape and material strength. They are commonly used in industrial machinery, such as engines, compressors, and conveyors, where a reliable and efficient power transfer is required.

5. Noise and Vibration Dampening: V-belts have inherent dampening properties that help reduce noise and vibration in the power transmission system. This is beneficial for improving the overall efficiency and performance of the machinery.

Conclusion:
V-belts have a trapezoidal or V-shaped cross-section, which enables them to fit securely into pulley grooves and transmit power efficiently. The trapezoidal shape provides a larger contact area and better grip, reducing the chances of slippage. V-belts are widely used in various mechanical systems for their high power transmission capacity and flexibility.