Across a metallic conductor of non–uniform cross section a constant potential difference is applied. The quantity which remains constant along the conductor is
Current density
Current
Drift velocity
Electric field
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A resistor R and 2μF capacitor in series is connected through a switch to 200 V direct supply. Across the capacitor is a neon bulb that lights up at 120 V. Calculate the value of R to make the bulb light up 5 s after the switch has been closed. (log10 2.5 = 0.4)