There are two questions, I am unable to understand. both are from barron’s, are linked and explanation given is unclear.
- The following five length of thin wire, all of which have the same diameter and length, are connected in circuit to a battery. i. In which length of wire is the current greatest? ii. Which length of wire generates the greatest power? (A) 3m of nichrome wire (B) 3m of copper wire (C) 3m of lead wire (D) 3m of steel wire (E) 3m of iron wire
Answer of (i) is B I chose it. (ii) is A, I chose B here. because P=I^2R. can anybody explain why it is incorrect?
- Three wires of same length and cross-sectional area are connected in series to a battery. The wire are made of copper, iron and nichrome, respectively. The potential difference across the copper is (A) the same as that across the iron or nichrome (B) greater than that across the iron or nichrome (C) less than that across the iron or nichrome (D) greater than that across the iron but less than that across nichrome (E) greater than that across the nichrome but less than that across iron.
I chose C because copper has the least resistance, as current is constant so voltage drop depends on resistance, according to V=IR. But the answer is D. Why? If this so. then in the first question part (i) answer should be iron instead of copper. Least resistance means highest current right?
Please somebody explain it? I have SAT this week. HELP!!!