Worksheet: Electric Fields of Point Charges

In this worksheet, we will practice relating electric forces to electric fields and describing the electric field lines produced by groups of charges.

Q1:

A charged object produces an electric field strength of magnitude 1.05×10 N/C at a distance of 2.6 m from its center. Find the charge of the object. Use 8.988×10 N⋅m2/C2 for the value of Coulomb’s constant. Answer to two significant figures.

Q2:

An object with a charge of 1.5 C is at a point in an electric field where the field strength is 12 N/C. What is the magnitude of the force on the object?

Q3:

An object has a charge of 0.335 nC. At a point near the object, the strength of the electric field from the object has a magnitude of 5.65 N/C. Find the distance from the object to the point. Use 8.988×10 N⋅m2/C2 for the value of Coulomb’s constant. Answer to two significant figures.

Q4:

An object with a charge of 0.25 C is at a point in an electric field where the force exerted on it by the field is 16 N. What is the magnitude of the field strength at the point occupied by the object?

Q5:

A charged object is at a point in an electric field where the force exerted on it by the field is 0.015 N and the field strength at that point is 2.5 N/C in the same direction as the force on the object. What is the charge of the object?

Q6:

An object has a charge of 125 mC. Find the electric field strength 36 cm from the object. Use 8.988×10 N⋅m2/C2 for the value of Coulomb’s constant. Answer to two significant figures.

  • A2.5×10 N/C
  • B8.7×10 N/C
  • C3.1×10 N/C
  • D3.2×10 N/C
  • E8.7×10 N/C

Q7:

An object with a charge of 𝑞 is located near an object with a charge of 𝑞, as shown in the diagram. Which of the following sets of values of 𝑞 and 𝑞 are consistent with the field lines of the electric field that the objects produce?

  • A𝑞=2C, 𝑞=1C
  • B𝑞=2C, 𝑞=1C
  • C𝑞=1C, 𝑞=2C
  • D𝑞=1C, 𝑞=1C

Q8:

An object with a charge of 𝑞 is located near to two other objects with charges of 𝑞 and 𝑞, as shown in the diagram. Which of the following sets of rankings of the magnitudes of 𝑞, 𝑞, and 𝑞 are consistent with the field lines of the electric field that the objects produce?

  • A𝑞<𝑞 and 𝑞=𝑞
  • B𝑞<𝑞<𝑞
  • C𝑞=𝑞 and 𝑞<𝑞
  • D𝑞>𝑞>𝑞

Q9:

An object with a charge 𝑞 is located near objects with charges 𝑞 and 𝑞, as shown in the diagram. Which of the following sets of rankings of magnitudes of 𝑞, 𝑞, and 𝑞 are consistent with the field lines of the electric fields that the objects produce?

  • A𝑞 < 𝑞 < 𝑞
  • B𝑞 < 𝑞 < 𝑞
  • C𝑞 < 𝑞 < 𝑞
  • D𝑞 > 𝑞 > 𝑞

Q10:

An object with a charge 𝑞 is located near objects with charges 𝑞 and 𝑞, as shown in the diagram. Which of the following sets of values of 𝑞, 𝑞, and 𝑞 are consistent with the field lines of the electric field that the objects produce?

  • A𝑞=2C, 𝑞=2C, 𝑞=1C
  • B𝑞=1C, 𝑞=2C, 𝑞=2C
  • C𝑞=2C, 𝑞=1C, 𝑞=2C
  • D𝑞=2C, 𝑞=1C, 𝑞=2C
  • E𝑞=1C, 𝑞=2C, 𝑞=1C

Q11:

An object with a charge 𝑞 is located near objects with charges 𝑞 and 𝑞, as shown in the diagram. Which of the following sets of values of 𝑞, 𝑞, and 𝑞 are consistent with the field lines of the electric field that the objects produce?

  • A𝑞=2 C, 𝑞=1 C, 𝑞=2 C
  • B𝑞=2 C, 𝑞=2 C, 𝑞=1 C
  • C𝑞=1 C, 𝑞=1 C, 𝑞=2 C
  • D𝑞=2 C, 𝑞=1 C, 𝑞=1 C
  • E𝑞=2 C, 𝑞=2 C, 𝑞=1 C

Q12:

An object with a charge 𝑞 is located near objects with charges 𝑞 and 𝑞, as shown in the diagram. Which of the following sets of values of 𝑞, 𝑞, and 𝑞 are consistent with the field lines of the electric field that the objects produce?

  • A𝑞=1 C, 𝑞=1 C, 𝑞=1 C
  • B𝑞=2 C, 𝑞=1 C, 𝑞=1 C
  • C𝑞=1 C, 𝑞=1 C, 𝑞=1 C
  • D𝑞=1 C, 𝑞=1 C, 𝑞=2 C
  • E𝑞=1 C, 𝑞=1 C, 𝑞=1 C

Q13:

An object with a charge of 𝑞 is located near the objects with charges of 𝑞 and 𝑞, as shown in the diagram. Which of the following sets of values of 𝑞, 𝑞, and 𝑞 are consistent with the field lines of the electric field that the objects produce?

  • A𝑞=1 C, 𝑞=1 C, 𝑞=2 C
  • B𝑞=1 C, 𝑞=1 C, 𝑞=1 C
  • C𝑞=1 C, 𝑞=1 C, 𝑞=1 C
  • D𝑞=2 C, 𝑞=1 C, 𝑞=1 C
  • E𝑞=1 C, 𝑞=1 C, 𝑞=1 C

Q14:

Point 𝑃 is at a distance 𝑑=2.2m from a charge 𝑞=55mC and at a distance 𝑑=1.7m from a charge 𝑞=24mC, as shown in diagram (a). Charge 𝑞 is then replaced by charge 𝑞=12mC, as shown in diagram (b). Through what clockwise angle would the net electric field at 𝑃 in diagram (a) have to be rotated to point in the same direction that the field points at 𝑃 in diagram (b)? Answer to the nearest degree.

Q15:

Two charged objects are separated as shown in the diagram. The positively charged object has a charge of 1 C and the negatively charged object has a charge of 1 C. The squares in the diagram have side lengths of 1 m. The direction of the electric field is calculated at the points a, b, c, d, and e. The electric field direction angles are measured counterclockwise from the horizontal to the nearest degree.

What is the direction of the electric field at a?

What is the direction of the electric field at b?

What is the direction of the electric field at c?

What is the direction of the electric field at d?

What is the direction of the electric field at e?

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