Efficiency of Carnot engine can be expressed as _________.
1
\(\eta =\left( 1-\frac{{{Q}_{1}}}{{{Q}_{2}}} \right)\)
2
\(\eta =\left( 1-\frac{{{Q}_{2}}}{{{Q}_{1}}} \right)\)
3
\(\eta =\left( 1+\frac{{{Q}_{2}}}{{{Q}_{1}}} \right)\)
4
\(\eta =\left( 1+\frac{{{Q}_{1}}}{{{Q}_{2}}} \right)\)