This question was previously asked in

DRDO EE 2008 Official Paper

Option 3 : 190 mW

__Concept:__

1) Electrical Power, ( P ) in a circuit is the rate at which energy is absorbed or produced within a circuit.

2) A source of energy such as a voltage will produce or deliver power while the connected load absorbs it.

NOTE: The higher their value or rating in watts the more electrical power they are likely to consume.

Mathematically power is represented as:

P = V × I

P = V2/R

P = I2 × R

Power triangle is shown below

Tellegen's theorem

Power delivered by source = Power absorbed by all elements

__Calculation:__

Given amplifier supply 12 V

AC voltage of 10 V peak then signal is V(t) = Vmsin(ωt) or V(t) = Vmcos(ωt)

Vm = 10 V

Load resistance is 1 KΩ

RMS value of the sinusoidal signal is

\({V_{rms}} = \frac{{{V_m}}}{{\sqrt 2 }}\)

Power delivered by the amplifier is

P = 12 V × (10 + 10) mA

P = 240 mW

Power absorbed by the load

\(P = \frac{{V_{rms}^2}}{R}\)

\({P_L} = \frac{{{{\left( {\frac{10}{{\sqrt 2 }}} \right)}^2}}}{{1\;K{\rm{\Omega }}}}\)

PL = 50 mW

Dissipated power is

Pdis = 240 mW – 50 mW

Pdis = 190 mW