A well machined steel plate of thickness $$L$$ is kept such that the wall temperature are $${T_h}$$ and $${T_c}$$ as shown in the figure below. A smooth copper plate of the same thickness $$L$$ is now attached to the steel plate without any gap as indicated in the figure below. The temperature at the interface is $${T_i},$$ The temperature of the outer walls are still the same at $${T_h},$$ and $${T_c}.$$ The heat transfer rates are $${q_1}$$ and $${q_2}$$ per unit area in the two cases respectively in the direction shown. Which of the following statements is correct?

Two $$8$$ $$mm$$ thick steel plates are placed $$5$$ $$mm$$ apart and welded by a butt joint. Welding is carried out at $$20$$ $$V$$ and speed of $$5$$ $$mm/sec.$$ Heat transfer efficiency is $$0.80.$$ If the heat required to melt steel is $$10$$ $$J/m{m^3}$$ and melting efficiency is $$0.625.$$ The weld current (in Amperes) will be

Match List - I (welding problems) with List - II (Causes) and select the correct answer using the codes given below the lists:

Consider the following statements :

The magnitude of residual stresses in welding depends upon
$$1.$$ Metal melted / deposited
$$2.$$ Design of weldment
$$3.$$ Support and clamping of components
$$4.$$ Welding process used

Which of the statements given above are correct?