An ammeter reads a current of 30 A when it is connected across the terminals of a cell of emf 2 V. Neglecting the meter resistance, find the amount of heat (in calories) in cell in 20 seconds.
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Here, `I = 30A, V = 2V, t=20s`. Let r be the internal resistance of a cell. Then `r = epsilon/I = 2.0/30 = 1/15 Omega` Heat produced in cell, `H = (I^(2)rt)/(J)` `= ((30)^(2) xx (1//15)xx 20)/4.2 = 285.7` cals
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