An electric bulb is rated 220 V and 100 W. When it is operated on 110 V, the power consumed will be –

(a) 100 W (b) 75 W (c) 50 W (d) 25 W

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  1. Class 10
  2. Chapter 12 Class 10 - Electricity

Transcript

NCERT Question 3 An electric bulb is rated 220 V and 100 W. When it is operated on 110 V, the power consumed will be - (a) 100 W (b) 75 W (c) 50 W (d) 25 W Explanation: The resistance of the bulb would remain constant even when voltage supply is changed. Given Potential difference = V = 220 V Power = P = 100 W Finding resistance We know that P = V I Putting I = ๐‘‰/๐‘… P = V ร— ๐‘‰/๐‘… P = ๐‘‰^2/๐‘… R = ๐‘‰^2/๐‘ƒ R = (220)^2/100 R = (220 ร— 220)/100 R = 22 ร— 22 R = 484 ฮฉ When V = 110 V Pโ€™ = ๐‘‰^2/๐‘… Pโ€™ = (110)^2/484 P = (110 ร— 110)/484 P = 12100/484 P = 1100/44 P = 100/4 P = 25 W Correct answer is (d) 25 W

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Davneet Singh
Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 9 years. He provides courses for Maths and Science at Teachoo.