JEE Main202127 Jul 2021Morning ShiftPhysicsCurrent ElectricityActual
In the given figure, a battery of emf E is connected across a conductor P Q of length l and different area of cross-sections having radii r 1 and r 2 r 2 < r 1 . Choose the correct option as one moves from P to Q .
Options
- ADrift velocity of electron increases.
- BElectric field decreases.
- CElectron current decreases.
- DAll of these
Correct answer
A. Drift velocity of electron increases.
Step-by-step solution
Current is constant in conductor i = constant Resistance of element d R = ρ d x π r 2 d V = i d R =  ipdx  π r 2 E = d V d x = i ρ π r 2 and V d = e E τ m ∴   V d × E → E ∝ 1 r 2 If r decreases, E will increase. ∴   V d will increase.