Electrostatics Review

Home » StickMan Physics » Unit 7: Electrostatics » Electrostatics Review

Review some basic electrostatics content and equations with our practice problems that review the basics of our electrostatics unit.

You can click on see answer to quickly check an answer or see a more detailed explanation and the the work to any problem by watching the video here.

Electrostatics Practice Problems

Would you have and attraction or repulsion with the following charge +6 C and +5 C

Repulsion, same charge sign

Would you have and attraction or repulsion with the following charge +6 C and -5 C

Attraction, opposite charge sign

What would be the charges on each of the unknown spheres? (draw the charge symbol next to the numbers below)

2 +

3 +

4 -

Would the following increase or decrease electrostatic force between two charged objects

________Doubling the charge on an object

Increase

________Doubling the distance between objects

decrease

________Halving the charge on one object

decrease

________Doubling the charge on one object and doubling the distance between the objects

decrease

How much would the electrostatic force change if you doubled one charge and tripled the distance between objects?

0.222 times

How would you describe the relationship between force and charge using Coulombs Law?

directly proportional

How would you describe the relationship between force and distance using Coulombs Law?

inversely squared proportional

What are the similarities and differences between the Electrostatic force and gravitational force calculated with the equations below?

Similarities:

They both are used to calculate a field force (A field force does not require contact)
Both forces have an inverse square relationship to distance
They are both related by a constant

Differences:

Force of gravity is always attractive
Electrostatic force can be either attractive or repulsive
Gravities constant is very small since gravity is a very weak force
Fg relates force created by masses, Fel relates force created by charges

What is an electrical conductor?

A material with freely flowing electrons

What is an electrical insulator?

A material that does not allow for electrons to freely flow

Draw the electrical fields around the point charge or point charges

Describe what causes and is occurring when someone gets shocked

A person is charged negatively because they have extra electrons, or positively if they have fewer electrons.

The actual shock occurs when the charge is grounded as electrons transfer to neutralize the charge.

Describe what causes you hair to stand up when charged

After being charged the same the hairs repel trying to stay away from each other. Straight up is where the repelling charged hairs separates the most.

An object becomes negatively charged when ___________ move __________ the object.

electrons, on to

An object becomes positively charge when ____________ move ___________ the object.

electrons, away from

Describe charging by friction

Different materials have a different affinity for electrons.

Some hold on to their electrons tighter than others.

Greater affinity for electrons: hold electrons stronger and often gain electrons by friction and become negative.

Less affinity for electrons: hold electrons weaker and often loose electrons by friction becoming positive

Provide two examples of material rubbed together and the charges that would result on each using the electron affinity table.

PVC and Silk rubbed together

PVC – and silk +

Paper and Hair rubbed together

Paper – and hair +

Describe charging by induction

Charging with no contact, temporarily causing an opposite charge

Describe charging by conduction

Contact with contact, permanently adding or receiving electrons, creating the same charge on the new object

What must be done to store electrical potential energy?

Work must be done to move a charge toward a similarly charged object or work must be done to move a charge away from an oppositely charged object

Describe electrical potential and how it is different than electrical potential energy?

Electrical potential, potential difference, or voltage, is the potential energy in a single charge

Electrical potential energy is the overall potential energy of the entire charged object

A 7.5x10^-7 C charge is placed 2. 0x10^-2 m away from a 2.1x10^-6 C charge. Find the electrostatic force that these two charges exert on each other.

35.4 N

How far away is a charge of 1.4x10¹ C from a 4.0x10¹ C charge when there is a force of 5.1x10⁸ N between them?

99.4 m

What is the magnitude of the electric field that produces a force of 1.1x10^-7 N on a charge of 5.0x10^-10 C?

E=220 N/C

How much potential energy is requires to send 2.19x10⁴ C of charge to create a voltage of 1.7x10¹ V?

𝑃𝐸=3.72𝑥10⁵ 𝐽

How much force would be on charge A in the diagram below and in what direction?

3.69𝑥10¹⁰ 𝑁 𝑅𝑖𝑔ℎ𝑡

Electrostatics Review

Electrostatics Practice Problems

Links