Electric current is passing through a solid conductor PQ from P to Q the electric current densities at P and Q are in the ratio
current density (J) of p= i/pi(4R)^2
Current density of q=i/pi(R)^2
Then , current density of p÷current density of q
Jp/Jq = i/pi(4R)^2×pi(R)^2/i
= 1/4
Thus , the answer is 1:4
Current density of q=i/pi(R)^2
Then , current density of p÷current density of q
Jp/Jq = i/pi(4R)^2×pi(R)^2/i
= 1/4
Thus , the answer is 1:4