I have read that the voltage source and current source absorbs power. My question is those sources are there to deliver voltage and current. Then, why they are absorbing power apart from doing their job. Please explain in detail. There is no proper article available on the internet about this question.
Do you know ohm's law?
Do you know how power is converted to heat dissipation?
Power sources (voltage and/or current) have internal resistance or impedance. A generator has resistance of the coils, for example. When the generator/source is connected to a load the current passes through the coils of the generator and dissipates heat due to the current of the circuit.
Same is true of a dc battery; it has internal resistance. When connected to a load the current passing through the battery causes power loss. The object of a battery is to keep the internal resistance as low as possible so as to minimize the neat losses.
Let me know if this does not adequately answer your question.