A circuit has a line of 5 A. How many lamps of rating 40 W, 200 V can simultaneously run on this line safely?

 

Answer:

Given,

  • Potential difference of one lamp, V = 200 V
  • Power of each lamp, P = 40 W
  • Total safe current, I = 5A 

Safe current through each lamp, 

i = P / V 

  = 40 / 200

  = 0.2 A

Therefore number of lamps that can be safely used,

n = I / i 

   = 5 / 0.2

    = 25

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CA Maninder Singh is a Chartered Accountant for the past 14 years and a teacher from the past 18 years. He teaches Science, Economics, Accounting and English at Teachoo