Correct Answer - Option 3 : Indicated power
Explanation;
Indicated Power:
It is the actual power developed inside the engine cylinder.
\(ip = \frac{{{p_m}LAN.n}}{{60}}\)
Brake Power:
This is the actual power available at the crankshaft and may be called the power output of the engine. It is always less than indicated power.
\(BP = \frac{{2\pi NT}}{{60}}\)
Mechanical efficiency is defined as the ratio of brake power (delivered power) to the indicated power (power provided to the piston).
It can be defined as the ratio of the brake thermal efficiency to the indicated thermal efficiency.
\({\eta _m} = \frac{{bp}}{{ip}} = \frac{{bp}}{{bp + fp}}\)
Indicated thermal efficiency :
It is the ratio of IP to fuel power.
\({\eta _i} = \frac{{ip}}{{{{\dot m}_f} \times CV}}\)
Brake thermal efficiency :
It is the ratio of bp to fuel power.
\({\eta _b} = \frac{{bp}}{{{{\dot m}_f} \times CV}}\)