Worksheet: Uniform Electric Field

In this worksheet, we will practice calculating forces exerted on charges by uniform electric fields and describing charge distributions producing such fields.

Q1:

Two thin parallel conducting plates are placed 2.0 cm apart. Each plate has sides of lengths 2.0 cm. One plate carries a net charge of +8.0 µC and the other plate carries a net charge of 8.0 µC.

What is the charge density on the inside surface of each plate?

What is the magnitude of the electric field between the plates?

  • A 1 . 5 × 1 0 N/C
  • B 1 . 9 × 1 0 N/C
  • C 2 . 3 × 1 0 N/C
  • D 2 . 1 × 1 0 N/C
  • E 1 . 1 × 1 0 N/C

Q2:

Two parallel plates with sides of length 10 cm are separated by 1.5 mm. Both plates given charges of magnitude 5.0×10 C, one plate positively charged and the other plate negatively charged. What is the electric field at the center of the region between the plates?

  • A 5 . 2 × 1 0 N/C
  • B 5 . 7 × 1 0 N/C
  • C 5 . 0 × 1 0 N/C
  • D 5 . 9 × 1 0 N/C
  • E 5 . 4 × 1 0 N/C

Q3:

The figure shows a small sphere of mass 0.25 g that carries a charge of 9.0×10 C. The sphere is attached to one end of a very thin silk string 5.0 cm long. The other end of the string is attached to a large vertical conducting plate that has a charge density of 30×10 C/m2. What is the angle that the string makes with the vertical?

Q4:

Two aluminum foil squares of side length 10 cm and thickness of 0.10 mm face each other. The squares a separated by 5.0 mm. One of the foils has a charge of +30 µC and the other has a charge of 30 µC.

Find the charge density for the surfaces of the foil squares that are facing toward each other.

  • A + 2 . 3 × 1 0 C/m2
  • B + 3 . 0 × 1 0 C/m2
  • C + 3 . 9 × 1 0 C/m2
  • D + 4 . 6 × 1 0 C/m2
  • E + 1 . 2 × 1 0 C/m2

Find the charge density for the surfaces of the foil squares that are facing away from each other.

  • A 1 . 2 × 1 0 C/m2
  • B 3 . 0 × 1 0 C/m2
  • C 6 . 0 × 1 0 C/m2
  • D 2 . 6 × 1 0 C/m2
  • E 4 . 2 × 1 0 C/m2

Find the magnitude of the electric field between the plates near the centers of the foil squares, assuming planar symmetry.

  • A 4 . 4 × 1 0 N/C
  • B 5 . 3 × 1 0 N/C
  • C 4 . 8 × 1 0 N/C
  • D 3 . 9 × 1 0 N/C
  • E 3 . 4 × 1 0 N/C

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