1 volt = 1 joule per coulomb
40 volts = 40 joules per coulomb
(40 joules per coulomb) x (80,000 coulombs) = 3.2 million joules of energy.
How fast or slow it happens is irrelevant.
The heat produced when 80,000 coulombs of charge is transferred through a potential difference of 40 volts is 3.2 million joules. The calculation uses the formula for electrical energy, which is the product of charge and voltage. The time taken for the transfer does not affect the total energy produced.
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