# Latest Interview Questions in Mechanical | Mechanical Engineering Interview Questions and Answers | Mechanical Engineer Job Interview Questions | Latest Placement Papers | Mechanical Engg Questions

1. What is the importance of the Thermodynamics in the field of Mechanical Engineering?
All the mechanical engineering systems are studied with the help of thermodynamics. Hence it is very important for the mechanical engineers.

2. How many Laws of Thermodynamics are there?
There are three laws of the thermodynamics.

First Law: Energy can be neither created nor destroyed. It can only change forms.In any process in an isolated system, the total energy remains the same.

Second Law: When two isolated systems in separate but nearby regions of space, each in thermodynamic equilibrium in itself, but not in equilibrium with each other at first, are at some time allowed to interact, breaking the isolation that separates the two systems, and they exchange matter or energy, they will eventually reach a mutual thermodynamic equilibrium. The sum of the entropies of the initial, isolated systems is less than or equal to the entropy of the final exchanging systems. In the process of reaching a new thermodynamic equilibrium, entropy has increased, or at least has not decreased.

Third Law: As temperature approaches absolute zero, the entropy of a system approaches a minimum.

3. State Laws of conservation of energy?
According to the laws of conservation of energy, “energy can neither be created nor be destroyed. It can only be transformed from one form to another.”

4. Is the boiler a closed system?
Yes definitely the boiler is a closed system.

5. What is Carnot engine?
It was being designed by Carnot and let me tell you that Carnot engine is an imaginary engine which follows the Carnot cycle and provides 100% efficiency.

6. Which formula forms a link between the Thermodynamics and Electro chemistry?
Gibbs Helmholtz formula is the formula which forms the link between the thermodynamics and electromagnetism.

∆Hs/R = [∂ lnp /∂ (1/T)]x

where: x – mole fraction of CO2 in the liquid phase
p – CO2 partial pressure (kPa)
T – temperature (K)
R – universal gas constant
α – mole ratio in the liquid phase (mole CO2 per mole of amine)

7. Which is the hardest compound known?
Diamond.

8. What is Hess Law?
According to the Hess law the energy transfer is simply independent of the path being followed. If the reactant and the product of the whole process are the same then same amount of energy will be dissipated or absorbed.

9. Which has more efficiency: Diesel engine or Petrol engines?
Off course Diesel engine has the better efficiency out of two.

# What is WLAN

WLAN, which stands for Wireless Local Area Network, is the technology of networking of a number of computers with each other without requiring the usage of wires. Due to a number of WLAN’s advantages such as ease of installation, convenience, deployment, mobility, expandability, productivity and cost, the popularity of WLAN has increased among home users. Wireless access is now offered as a service, paid or sometimes free, to customers of public businesses such as coffee shops or shopping malls.

Development began in 1970, when a computer communication network using inexpensive ham-like radios called ALOHAnet was created by the University of Hawaii. It features bi-directional star topology, with seven computers deployed over four islands. The central computer, located in Oahu Island, communicated with the other computers without using phone lines.

In 1980, amateur radio operators developed the first generation of wireless data modems. They accomplished this by adding a voice band data communication modem, which had data rates below 9600 bps, to an existing short distance radio system. In 1991, the Institute of Electrical and Electronics Engineers (IEEE) held the first IEEE Workshop on WLAN, with the objective of evaluating alternative technologies. At the same time, the IEEE 802.11 committee was working on developing a standard for WLANs.

Orthogonal Frequency Division Multiplexing (OFDM), also known as spread-spectrum modulation technology, is used in WLANs to enable communication between devices in a limited area or basic service set (BSS), which is the set of all stations that can communicate with each other. OFDM is a radio wave-based technology. Through this technology, users are able to move around a broad coverage area while remaining connected to a wireless network.

BSS has two types. Independent BSS contains no access points, meaning that it is an ad-hoc network that is unable to connect with other basic service sets. Unlike Independent BSS, Infrastructure BSS is able to communicate with other stations through access points.

There are three types of WLANs. The first, peer-to-peer (P2P), enables wireless devices to directly communicate with each other without requiring the involvement of central access points. The second WLAN type, which is a bridge, connects networks of different types, such as a wireless network to a wired Ethernet network. The third type is the wireless distribution system, where access points are used as repeaters in place of connecting all access points in a network using wires.

WLAN does have its disadvantages. In terms of security, WLANs are more prone to unwanted eavesdropping by a third party, since WLAN transceivers communicate using radio frequencies. Wireless packets can be intercepted by a nearby computer, and they may be picked up at a distance by a user with a good quality antenna. “Wardrivers” is a term referring to computer users who locate and crack into wireless networks.

WLAN networking signals may be subject to interference and complex propagation effects like multipath or Ricidian fading. WLANs also tend to have a limited range, requiring repeaters or additional access points in order to achieve greater range. They also have a slow data transmission rate of 1 – 108 Mbps, compared to wired networks which can run at rates of 100 Mbps to several Gbps. The built-in congestion avoidance of Transmission Control Protocol (TCP) hindered the transmission speed of wireless networks.