Electric Charge and Particles Overview

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Questions and Answers

What is the term for the phenomenon in which amber attracts small objects after being rubbed?

Nuclear fusion

Gravitational pull

Magnetic induction

Electrostatic attraction (correct)

What does the conservation of electric charge state about a closed system?

The net charge of a closed system fluctuates randomly.

The net charge of a closed system remains constant. (correct)

The net charge of a closed system always increases.

The net charge of a closed system always decreases.

An object with an equal amount of positive and negative charge is considered to be what?

Negatively charged

Positively charged

Polarized

Electrically neutral (correct)

What is the symbol for the elementary charge?

e Signup and view all the answers

What is the magnitude of charge on a proton, in Coulombs?

+1.602 × 10⁻¹⁹ C Signup and view all the answers

What is the mass of a neutron?

1.675 × 10⁻²⁷ kg Signup and view all the answers

If two objects have like charges, what type of force will they exert on each other?

Repulsive force Signup and view all the answers

What does 'polarization' refer to in the context of electric charge?

The separation of positive and negative charge within an object Signup and view all the answers

What is the term for an object that has regions of positive and negative charge separated within it, even if the net charge is zero?

Polarized Signup and view all the answers

Which of the following best describes a material where charge can move easily?

Electric conductor Signup and view all the answers

What happens to a charged conductor when it is grounded?

The charge is neutralized and spreads out Signup and view all the answers

When a charged rod is brought near a neutral piece of paper, which of these events happen?

The paper becomes polarized but maintains a neutral charge Signup and view all the answers

What happens to the leaves of a negatively charged electroscope when you touch its bulb with your hand?

The leaves fall down Signup and view all the answers

Which of the following is NOT a property of water due to hydrogen bonding?

Low surface tension Signup and view all the answers

If a neutral conductor is grounded while a charged object is held near it, what will result?

The conductor will become charged opposite to the nearby object. Signup and view all the answers

If a glass rod rubbed with silk is brought near the bulb of a neutral electroscope without touching it, what happens to the leaves?

The leaves become polarized and spread apart. Signup and view all the answers

What happens to the leaves if a positively charged rod touches the bulb of an electroscope that was originally neutral?

The leaves will spread further apart due to an excess of positive charge on the leaves Signup and view all the answers

How do semiconductors compare to conductors and insulators in terms of charge movement?

Semiconductors allow charge to move much less easily than conductors but more easily than insulators. Signup and view all the answers

Study Notes

Electric Charge

Amber, when rubbed, becomes charged, attracting small objects. This process transfers electric charge between the amber and the rubbing material.
Electric charge is conserved—the net charge of a closed system remains constant.
Electric forces can be attractive or repulsive. There are two types of charge: positive and negative.
Net charge is the algebraic sum of all charges in a system.
A neutral object has equal amounts of positive and negative charges, resulting in a net charge of zero.

Elementary Charge

The magnitude of a proton's or electron's charge is the elementary charge (e).
Any object's net charge is always a whole-number multiple of the elementary charge.

Proton, Electron, and Neutron

| Particle | Mass (kg) | Electric Charge (C) |
|---|---|---|
| Proton | 1.673 × 10⁻²⁷ | +1.602 × 10⁻¹⁹ |
| Electron | 9.109 × 10⁻³¹ | −1.602 × 10⁻¹⁹ |
| Neutron | 1.675 × 10⁻²⁷ | 0 |

Charge Transfer Example

A typical charge transferred when interacting (e.g., walking across a carpet) is about 1 nC.
If transferred only by electrons, calculate the number of electrons transferred.
Estimate the percentage of excess electrons in an object with a −1 nC net charge.

Attraction, Repulsion, and Polarization

Like charges repel, unlike charges attract.
Polarization is a separation of positive and negative charges within a neutral object, although the net charge remains zero.
A polarized object can experience a force from an external electric field even if it's uncharged.

Induction and Polarization

A neutral object can be polarized by an external charge. This polarization can create a net force if the external charge is present. This is called polarization by induction.

Polarized Molecules and Materials

Some molecules, notably water, are intrinsically polarized.
Materials differ in how easily charges move within them. Conductors allow easy charge movement, insulators resist charge movement, and semiconductors are intermediate.

Charging Insulators and Conductors

Rubbing different insulators together can transfer electrons and charges, creating charged objects.
Touching a charged insulator to a conductor can transfer charge, and this process can be repeated to build more charges.
Grounding a conductor allows charge to flow to a large, neutral object (like the Earth), discharging the conductor.
If a conductor is grounded near a charge, charge transfer may occur to or from the grounded object.

Charging Conductors by Induction

An initially neutral conductor can be charged by grounding it while a charge is nearby.

Electroscope Example

A negatively charged electroscope with separated leaves demonstrates the principles of charge interaction.
Touching the electroscope's bulb and then bringing a positive charge near the bulb causes polarization of the electroscope.
Adding the positive charge directly to the bulb increases the net positive charge causing greater foil separation.

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Description

This quiz explores the fundamentals of electric charge, including the processes of charge transfer and the nature of positive and negative charges. It also covers the basic properties of protons, electrons, and neutrons, highlighting their masses and charges. Test your understanding of these core concepts in electricity and particle physics.