Asphere of 200 mm diameter made of cast iron initially at uniform temperature of 400 °c is quenched into oil. the oil bath temperature of 40 °c. if the temperature of the sphere is 100 °c after 5 minutes, find the heat transfer coefficient on the surface of the sphere. take cp (cast ron) 0.32 kj/kg °c, p neglect internal thermal resistance [ans. 134 kw/m2 °c] 3 (cast ron) -7000 kg/m

gold is my favorite solid.

answer is: nuclear fusion produces elements that are heavier than helium.

nuclei combine to form a heavier nucleus, releasing energy.  

for example, fusion of hydrogen atoms at the sun.  

this fusion nuclear reaction is in the inner core of the sun and hydrogen (atomic number 1) is conveted into helium (atomic number 2).  

the inner core is the central region of the sun and all solar energy is produced in the core by nuclear fusion.