Coulomb's Law Questions

Coulomb's Law

Questions about radial electric fields

Multiple Choice

The electric field strength at a distance of 2.0 × 10^–8 m from a nucleus is 3.3 × 10⁸ N C^–1.

What is the charge on the nucleus?

• 1.6 × 10^–19 C

• 1.5 × 10–17 C

• 7.3 × 10^–10 C

• 3.8 × 10^–9 C

Multiple Choice

Which is the correct distance to use when determining the electric force between the charged spheres?

• z

• x + z

• y + z

• x + y + z

Open Ended

Explain why the direction of the resultant electric field strength at point X is to the left.

ANSWER

• The direction of the electric field due to the negative charge is to the left and right for the positive charge.

• The magnitude of the electric field strength due to the positive charge is smaller than that for the negative charge (because of greater distance).

• (Hence the resultant electric field strength is to the left.)

Fill in the Blank

The separation between the centres of two oppositely charged ions is 3.0 × 10⁻¹⁰ m. Each ion has charge of magnitude 1.6 × 10⁻¹⁹ C. Calculate the minimum energy in eV required to completely separate the ions to two significant figures.

Fill in the Blank

The electric potential at point X is +1800 V. Calculate the electric potential V at the surface of the sphere in volts and two two significant figures.

Fill in the Blank

The potential at the surface of the sphere is 5400 V and the radius is 4.0 cm. Calculate the charge Q on the sphere in μC to two significant figures.

Fill in the Blank

The charge on the sphere is 24 μC and the radius is 4.0 cm. Calculate the electric field strength E at the surface of the sphere in kNC^-1 to two significant figures.

Open Ended

Each sphere has mass 6.0 × 10^–5 kg and charge –4.0 × 10^–9 C. The separation between the centres of the spheres is 2.0 cm.

Explain why the spheres are separated as shown.

Fill in the Blank

Each sphere has mass 6.0 × 10^–5 kg and charge –4.0 × 10^–9 C. The separation between the centres of the spheres is 2.0 cm.

Calculate the angle θ made by each thread with the vertical in degrees to two significant figures.