alleryStart learning →Household mains is quoted as 120 V AC. What is its peak voltage?
A85 V
B120 V
C240 V
D170 V
Answer & Solution
Correct answer: D. 170 V
1. A quoted mains figure is the rms voltage, so V_rms = 120 V.
2. The peak and rms values are linked by V_rms = V_0 divided by the square root of two.
3. Rearranging gives V_0 = 1.414 times V_rms.
4. Substituting: V_0 = 1.414 (120 V) = 170 V.
5. 85 V is the trap of dividing by 1.414 instead of multiplying.
_Source: OpenStax College Physics (CC BY 4.0), Ch 20 "Electric Current, Resistance, and Ohm's Law", section Alternating Current_
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