Question 3 Page 218 An electric iron of resistance 20 takes a current of 5 A. Calculate the heat developed in 30 s. Resistance = R = 20 Ω Current = I = 5A Time taken = t = 30 s We know that, Heat generated is given by H = I2 R t H = (5)2 × 20 × 30 H = 25 × 20 × 30 H = 25 × 600 H = 15000 H = 15 × 103 H = 1.5 × 10 × 103 H = 1.5 × 104 J Heat generated is 1.5 × 104 J

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Maninder Singh

CA Maninder Singh is a Chartered Accountant for the past 13 years and a teacher from the past 17 years. He teaches Science, Economics, Accounting and English at Teachoo

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