A 40W instrument has a resistance 90 Ohms. On what voltage should it be operated normally
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Correct Answer: Option A
Explanation:
P = 40W
 R = 90W
 V = ?
 P = \(\frac{V^2}{R}\)
 V\(^2\) = PR = 40 x 90
 V\(^2\) = 3000
 V = √3600
 V = 60N
P = 40W
 R = 90W
 V = ?
 P = \(\frac{V^2}{R}\)
 V\(^2\) = PR = 40 x 90
 V\(^2\) = 3000
 V = √3600
 V = 60N