Worksheet: Electric Potential of a Charged Disk

In this worksheet, we will practice calculating the absolute electric potential at a given position relative to a charged disk.


A CD disk of radius 𝑅=3.0cm is sprayed with a charged paint so that the charge varies continually with radial distance π‘Ÿ from the center in the following manner: 𝜎=βˆ’6.0/ο€»π‘Ÿπ‘…ο‡Cm.

Find the potential at a point 4.0 cm above the center.


A thin conducting plane has a charge density of βˆ’9.0Γ—10 C/m2. An electron is placed 0.80 cm above the the plane. What is the magnitude of the acceleration of the electron?

  • A3.0Γ—10 m/s2
  • B36Γ—10 m/s2
  • C3.2Γ—10 m/s2
  • D2.9Γ—10οŠͺ m/s2
  • E25Γ—10 m/s2


Two square conducting plates of side length 50.0 cm are placed parallel to each other 9.0 mm apart. What magnitude electric field is generated between the plates after 10 electrons are transferred from one plate to the other?

  • A3.2Γ—10 N/C
  • B96Γ—10 N/C
  • C74Γ—10 N/C
  • D7.2Γ—10 N/C
  • E3.6Γ—10 N/C


A proton moves horizontally at an initial speed 𝑣=8.0Γ—10/ms directly toward a large, positively charged plate that has a surface charge density of 9.0Γ—10 C/m2. What is the proton’s horizontal displacement from the plate at the point where it comes instantaneously to rest?

  • A9.3Γ—10 m
  • B41Γ—10 m
  • C4.5Γ—10 m
  • D98Γ—10 m
  • E65Γ—10 m


A thin conducting plate 4.00 m on a side is given a total charge of βˆ’18.0 Β΅C. A point 𝑃 is located at the center of the plate 2.00 cm above its surface.

What is the magnitude of the electric field at the point 𝑃?

  • A6.35Γ—10οŠͺ N/C
  • B63.3Γ—10οŠͺ N/C
  • C98.1Γ—10οŠͺ N/C
  • D234Γ—10οŠͺ N/C
  • E97.5Γ—10οŠͺ N/C

What is the magnitude of the electric force on an electron at the point 𝑃?

  • A456Γ—10οŠͺ N
  • B125Γ—10οŠͺ N
  • C1.02Γ—10οŠͺ N
  • D325Γ—10οŠͺ N
  • E3.25Γ—10οŠͺ N

An electron is moved 1.00 cm vertically downward from the point 𝑃. What is the work done by the electric field on the electron?

  • A30Γ—10 J
  • B1.02Γ—10 J
  • C1.02Γ—10 J
  • D125Γ—10 J
  • E1.02Γ—10οŠͺ J

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