A copper wire of length 1 m and radius 1 mm is joined in series with an iron wire of length Z m and radius 3 mm and a current is passed through the wires. The ratio of the current density in the copper and iron wires is

see full answer

Talk to JEE/NEET 2025 Toppers - Learn What Actually Works!

Real Strategies. Real People. Real Success Stories - Just 1 call away

An Intiative by Sri Chaitanya

18 : 1

9 : 1

6 : 1

2 : 3

answer is B.

(Unlock A.I Detailed Solution for FREE)

Ready to Test Your Skills?

Check your Performance Today with our Free Mock Test used by Toppers!

Take Free Test

Detailed Solution

Current density J=iA = iπr2 ⇒ J1J2 = i1i2 × r22r12But the wires are in series, so they have the samecurrent, hence i1=i2. So J1J2 = r22r12=9:1

Watch 3-min video & get full concept clarity