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Nilanjan Bhowmick AIR 3, CSIR NET (Earth Science)
Ghost.
To understand this you have to understand flow of electron cause current run through the circuit, electrons are never consumed during their path, but you have to give energy to electron in order to make them run in circuit, and that energy is e*V ( voltage) . so a source connected in circuit does provide electron in exchange of energy then after completion of path these electron are collected back by source as in a case of semiconductor electron hole pair create at one end and combine at other end, This is what i know i recommend you to read it more in case if i am wrong. Wishes