Electrostatics and Conductivity Quiz

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Questions and Answers

Which of the following best describes the behavior of charges in an irregularly shaped solid conductor?

Charge density is greatest where the surface curves least sharply.

Charges distribute evenly throughout the conductor.

Charge density is greatest where the surface curves most sharply. (correct)

Charges accumulate only at the center of the conductor.

What is the primary mechanism of charge transfer according to the electron-proton transfer model?

Transfer of both electrons and protons.

Simultaneous transfer of electrons and neutrons.

Transfer of protons from one atom to another.

Transfer of electrons from one atom to another. (correct)

What happens to the leaves of a metal leaf electroscope when it is charged?

The leaves remain hanging straight down.

The leaves first repel and then attract.

The leaves repel each other. (correct)

The leaves move closer together.

A neutral object is brought near a charged object. What is the expected interaction?

They will attract each other. Signup and view all the answers

What distinguishes a conductor from an insulator regarding electron behavior?

Electrons flow freely in conductors, but not in insulators. Signup and view all the answers

A negatively charged plastic rod is brought near a neutral object. How will electrons distribute on the rod?

Electrons will move to the end farthest from the neutral object. Signup and view all the answers

What is the symbol and unit for electric charge?

$q$ and Coulomb (C) Signup and view all the answers

How many elementary charges are in one Coulomb of charge?

$6.25 imes 10^{18}$ Signup and view all the answers

When two objects are rubbed together, what determines which object gains electrons and which loses them?

The material of which the objects are made and how strongly they hold onto electrons. Signup and view all the answers

What is the key difference between charging by conduction and charging by induction?

Conduction involves direct contact whereas induction doesn't involve direct contact. Signup and view all the answers

If a neutral electroscope is touched by a negatively charged rod, what charge does the electroscope gain?

The electroscope gains a negative charge. Signup and view all the answers

When a negatively charged rod is brought near a neutral electroscope, the leaves of the electroscope spread to a certain degree. What happens to this leaf spread if the negatively charged rod is then removed?

The leaves move closer together, returning to their original position. Signup and view all the answers

How can a neutral electroscope be permanently charged positively via induction?

By bringing a negatively charged rod near the electroscope, grounding the scope to enable a charge flow, then removing the rod. Signup and view all the answers

During the process of charging by conduction, what happens to the charge of the object used to charge the neutral object?

The object used to charge loses charge. Signup and view all the answers

What is the primary difference between charging an insulator and a conductor by contact?

The charge on a conductor will spread over its surface, while the charge on an insulator will remain at the point of contact. Signup and view all the answers

Which of the following is true regarding the net charge of an isolated system when any of the charging methods occur?

The net charge of the system remains constant. Signup and view all the answers

Study Notes

Electrostatics

All matter is composed of atoms
Protons are positive, electrons are negative, neutral objects have equal amounts of protons and electrons
Electrons move; protons do not
Excess electrons = negative charge
Deficit of electrons = positive charge
Like charges repel, unlike charges attract
Charge is conserved in a closed system
Unit of charge is the Coulomb (C), symbol q
1 Coulomb = 6.25 x 10¹⁸ protons or an equal number of electrons
Elementary charge (e) = 1.6 x 10^-19 C
Charge on one electron = -1.6 x 10^-19 C
Charge on one proton = +1.6 x 10^-19 C
Charge is quantized

Conductivity

Conductivity describes how easily electrons move through a material
Conductors allow electron flow easily (metals, ionic solutions)
Insulators do not allow electron flow easily (wood, plastics, glass)
Superconductors have extremely high conductivity

Increasing Conductivities

Negatively Charged Metallic Sphere: Electrons are free to move as far apart as possible
Negatively Charged Plastic Rod: electrons are forced to stay at one end of the rod since they aren't free to flow

Electroscopes

Instruments to detect charges
Metal leaf electroscope: Metallic knob, stem, insulating rubber stopper, glass box, metal foil
Neutral: Leaves hang straight down
Charged: Leaves repel each other (same charge)
Tin Foil Straw Electroscope: Straw hangs vertically when neutral, repels when charged

Methods of Charging

Charging by Friction: Objects gain or lose electrons when rubbed together (high electron affinity). Materials with a stronger hold on electrons will have a higher electron affinity. Materials listed on the top of the electrostatic series have a high electron affinity, meaning they will tend to acquire electrons and become negatively charged when rubbed against materials lower on the series. Materials listed lower tend to lose electrons when rubbed against materials on top, and become positively charged.
Charging by Contact (Conduction): Charging a neutral object by touching it with a charged object. The quantity of charge transferred depends on the size and shape of the objects. Same size objects = same charge; Bigger size object = bigger charge.
Charging by Induction: A charged object is brought near a neutral object. Electrons are attracted or repelled, shifting the charge distribution in the neutral object. This is a temporary charge separation, and only occurs if the object is grounded.

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Description

Test your understanding of electrostatics and conductivity concepts. This quiz covers the fundamental principles of charge, the behavior of electrons, and the properties of conductors and insulators. Ensure you grasp the intricacies of charge conservation and conductivity types.