A 40-W instrument has a resistance of 90\(\Omega\). On what voltage should it be operated normally?
A
60V
B
150V
C
225V
D
3600V
Verified Correct Answer: A.
Physical Principles & Numerical Solution
P = \(\frac{V}{R}\)
V = \(\sqrt{PR}\)
V = \(\sqrt{40 \times 90}\)
= 60V
Source: Myschool Past Questions Archive (Record #28016)