Verified Solution • 2025–26 Session moderate

QJEEM16Ph8d39: JEE Main 2016 Physics - Class 12 JEEM16Ph8d39 Solution: The potential (in volts) of a charge distribution is given by.…

The potential (in volts) of a charge distribution is given by.

V(z) = 30 − 5x2 for |z| ≤ 1 m.
V(z) = 35 − 10 |z| for |z| ≥1 m.

V(z) does not depend on x and y. If this potential is generated by a constant charge per unit volume ρ0 (in units of ε0) which is spread over a certain region, then choose the correct statement.

Multiple Choice Options

  • A ρ0 = 10 ε0 for |z| ≤ 1 m and ρ0=0 elsewhere
  • B ρ0 = 20 ε0 in the entire region
  • C ρ0 = 40 ε0 in the entire region
  • D ρ0 = 20 ε0 for |z| ≤ 1 m and ρ0=0 elsewhere

Step-by-Step Verified Solution

We know,

E(z) = − dvdz

∴   E(z) = − 10 z for |z|≤1 m

and E(z) = 10 for |z|≥1 m

∴   The source is an infinity large non conducting thick of thickness z = 2 m.

∴   E = σ2ε0 = ρ(2)2ε0 = ρε0

∴   ρε0 = 10

⇒   ρ = 10ε0

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