https://www.shivameducation.org/2019/07/mechanical-engineering-model-question.html MECHANICAL ENGINEERING MODEL QUESTION &ANSWER ON WELDING TOPIC. 01. In arc welding operations the current value is decided by size of the electrode. SOLUTION:- current value is increase with size of the electrode. The smaller the diameter means it requires less current and it deposits a smaller amount of filler metal. 02. Two sheets of same material but different thickness can be butt welded by changing the size of one electrode. SOLUTION:- changing the size of one electrode is needed because both the thickness of weld is not same. 03. Welding units operate at what power factor? 0. 3. SOLUTION:- Welding transformer is highly inductive load, having a power factor of below 0.5. 04. Carburising flame is used to weld metals like aluminium, nickel, monel etc. SOLUTION:- The carburizing flame has excess acetylene, the innercone has a feathery edge extending beyond it. This white feather is called the acetylene feather. It is used for Aluminium, Nickel etc. 05. Preheating is required before welding for which material essentially ? cast iron. SOLUTION:- A cast iron is an alloy of iron, carbon, and silicon, in which the amount of carbon is usually more than 1.7% and less than 4.5%. The over all weldability of cast iron is low and depends on the material type, complexity, thickness, casting complexity and need for machinability. 06. Fluxes are used In welding in order to protect the molten metal and the surfaces to be joined from Oxidation. SOLUTION:- The primary purpose of flux is to prevent the oxidation of base and filler material. 06.Two stainless steel foils of 0.1 mm thickness are to be joined. Which of the following processes would be best suited TIG welding. SOLUTION:- Tungsten Inert Gas welding, is the best suited for welding sheets as thin as 0.1 mm-0.5mm thickness. 07. Stud and projection welding belong to the following category of welding resistance welding. SOLUTION:- Stud welding, also known as"drawn arc stud welding" joins a stud and another piece of metal together by heating both parts with an arc. 08. The strength of a properly welded joint as compared to base metal would be more. SOLUTION:- The strength of weld bead that is the portion which is welded is always higher and that is because of the Alloy formation. 09. Which of the following welding technique isused to make LPG cylinders? SAW. SOLUTION:- SAW (submerged arc welding) can produce long weldruns and used in joining thick plates in pressure vessels,bridges, LPG cylinders etc. 10. Among the given welding techniques, the minimum heat afrected zone is produced in A. seam welding B. solid state welding C. ultrasonic welding D explosive welding Correct Answer:- C. ultrasonic welding SOLUTION:- Ultrasonic welding produces least heat affected zone since it generates heat by high frequency vibration. 11. The correct sequence of the following processes in increasing order of their welding temperature is 1) Gas welding 2) Thermit welding 3) Arc welding 4) Resistance welding Answer:- 1, 2, 3, 4. SOLUTION:- Out of the given options Gas welding is done at the lowest temperature, It is performed at the temperature around 2000 °C, Thermit welding is done at a temperature in the range of 2200°C, then Arc welding is performed at a temperature around 3000°C to 20000°C, and in resistance welding two metals are fused at their welding point. 12. Projection welding is Multi-spot welding process. SOLUTION:- Projections are made on one sheet and those spot are used for spot welding. 13. In arc welding, arc is created between the electrode and work by contact resistance. 14. Too high welding current in arc welding would result in Excessive spatter, under cutting along edges, irregular deposits and wasted electrodes. 15. Which one of the following cutting tool bits are made by powder metallurgy process? Ceramic tool bits.