Question

An electric iron consumes energy at a rate of 840 w when heating is at the maximum rate and 360 w when the heating is at the minimum. The voltage is 220 v. What is the ratio of resistances in the two cases?

Answer 1

Answer:

R1 / R2  = 0.42

Explanation:

P1 = V² / R1                   &                 P2 = V² / R2

R1 = V² / P1                   &                 R2 = V² / P2

R1 = 220² / 840           &                 R2 = 220² / 360  

R1 = 57.61 ohm            &                 R2 = 134.44 ohm

R1 / R2  = 57.61 /  134.44

R1 / R2  = 0.42

Answer 2

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