Question

Given a sample of radium –226 having half - life of 4 days. Find the probability, a nucleus disintegrate after 2 half lives.

Answer 1

Conduction current is something you would witness in a conducting material, such as a metal. It refers to the movement of current in the presence of an electric field and can be described by Ohm's law. Convection current is current flow in an insulating medium. This, however, does not follow Ohm's law. We can define current as the electric charge passing through an area per unit volume. I = d Q d t I=dQdt per unit time. Current density is the amount of current flowing through a surface per unit time J = Δ I Δ S J=ΔIΔS with I = ∫ J ⋅ d S I=∫J⋅dS. In a convection current, we have a current flowing through an insulating medium Δ I = Δ Q Δ t = ρ Δ S Δ y Δ t = ρ Δ S u y ΔI=ΔQΔt=ρΔSΔyΔt=ρΔSuy where S is the surface the current is passing through, y is the length along the velocity vector, and u y uy is the velocity vector. So we can express the convection current as J y = Δ I Δ S = ρ ⋅ u y Jy=ΔIΔS=ρ⋅uy. Conduction current density will describe the ability for an electric field E to propagate through a medium, controlled by the proportionality constant sigma, or conductivity. So, both describe a "current", but it might be easier to replace the word "current" with "flow; convection describes the flow through an insulating medium, and conductivity describes flow through a conducting medium.

Reference https://www.physicsforums.com/threads/difference-between-conduction-convection-current-density.926676/