Electrostatic Forces in Materials
Physics ⇒ Electricity and Magnetism
Electrostatic Forces in Materials starts at 10 and continues till grade 12.
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See sample questions for grade 11
A dielectric is inserted between the plates of a charged parallel plate capacitor. What happens to the electrostatic force between the plates?
A plastic rod is rubbed with wool and becomes negatively charged. What happens to the electrons in this process?
A student rubs a balloon on their hair and the balloon sticks to a wall. Which force is responsible for this phenomenon?
Calculate the electrostatic force between two charges of +2 μC and -3 μC placed 0.2 m apart in air. (Take k = 9 × 109 N·m2/C2)
Describe what happens to the charges in a conductor when it is placed in an external electric field.
Describe what happens to the electrostatic force between two charges if the medium between them changes from air (εr ≈ 1) to glass (εr ≈ 5).
Explain the difference between conductors and insulators in terms of electron movement.
Explain why metals are good conductors of electricity.
Explain why the force between two charges is weaker in water than in air.
If the magnitude of each of two point charges is doubled, how does the electrostatic force between them change?
State Coulomb's law for the force between two point charges in a vacuum.
The electrostatic force between two charges is 9 N when they are 1 m apart. What will be the force if the distance is reduced to 0.5 m?
A charged sphere is suspended by an insulating thread and brought near a neutral metal sphere resting on an insulating stand. Describe and explain the sequence of charge movement and the final charge distribution if the metal sphere is briefly grounded while the charged sphere is nearby.
A parallel plate capacitor is filled halfway with a dielectric of relative permittivity εr and the other half with air. Describe qualitatively how the electric field and potential difference are distributed across the plates.
A parallel plate capacitor with air as the dielectric is connected to a battery and fully charged. The battery is then disconnected, and a dielectric slab is inserted between the plates. What happens to the voltage across the plates and the stored energy? Explain your answer.
A point charge q is placed at the center of a solid dielectric sphere of radius R and relative permittivity εr. Derive an expression for the electric field at a distance r < R from the center.
A slab of dielectric material with thickness t and relative permittivity εr is inserted between the plates of a parallel plate capacitor of plate separation d (t < d). If the original capacitance is C0, derive the new capacitance in terms of C0, t, d, and εr.
