2021 · Q4
An electric circuit is consisting of a cell, and ammeter and a nichrome wire of length l. If the length of the wire is reduced to half (l/2) then the ammeter reading
General KnowledgePhysics
- Adecreases to one-half.
- Bgets doubled.
- Cdecreases to one-third.
- Dremains unchanged.
Explanation
Resistance is directly proportional to length (R = rho*l/A), so reducing the nichrome wire's length to half halves its resistance. With the cell voltage unchanged, Ohm's law I = V/R means the current doubles when the resistance is halved. The ammeter therefore reads twice the original current. Neither a decrease nor an unchanged reading is consistent with R proportional to l.