(i) Describe the construction and working of a spark plug. Where it is used ? Why?

(ii) An engine working on Otto cycle, air has a pressure of \(1 \mathrm{bar}\) and temperature of \(27^{\circ} \mathrm{C}\) at the entry. Air is compressed adiabatically with a compression ratio of 7 . The heat is added at constant volume till the temperature rises to \(2000 \mathrm{~K}\). Find (1) Air standard efficiency (2) Heat supplied (3) Pressure and temperature at the end of compression (4) Mean effective pressure in \(\mathrm{kPa}\). Take \(\mathrm{R}=287 \mathrm{~J} / \mathrm{kg} . \mathrm{K}\) and \(\gamma=1.4\)