alleryAn electric iron at its lower setting uses 330 W on a 220 V supply. What is the resistance of the iron at this setting?
A146 Ω
B1.5 Ω
C73 Ω
D44 Ω
Answer & Solution
Correct answer: A. 146 Ω
1. First find the current: $I = \dfrac{P}{V} = \dfrac{330}{220} = 1.5$ A.
2. Then resistance: $R = \dfrac{V}{I} = \dfrac{220}{1.5}$.
3. $R = 146\ \Omega$.
4. The option 44 Ω is the resistance at the 1100 W higher setting, not the 330 W setting, so it is rejected.
_Source: Balbharati (Maharashtra Board) Class 10 Science & Technology, Ch 4 "Effects of Electric Current", p.59_
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