Physics Chapter 2: Observations and Predictions

Questions and Answers

What is the charge that appears on each conductor called?

Permanent charge

Static charge

Residual charge

Induced charge (correct)

What happens to the metal sphere when the positively charged glass rod is brought near without touching?

It remains neutral (correct)

It gains a negative charge

It gains a positive charge

It disintegrates

What is the effect of momentarily earthing the metal sphere while the glass rod is nearby?

Electrons are attracted from the earth (correct)

Positive charges leave the sphere

The sphere becomes positively charged

The sphere loses its induced charge

What observation is made when two glass rods are brought near each other without being rubbed?

They do not interact. Signup and view all the answers

What occurs when oppositely charged spheres produced by induction come into contact?

They become neutral Signup and view all the answers

How does the electrostatic force between two charged bodies change with distance?

It decreases with distance Signup and view all the answers

What happens when a glass rod is rubbed with silk?

The glass rod becomes positively charged. Signup and view all the answers

Which statement correctly describes the relationship between the charges and the electrostatic force?

Force is directly proportional to the product of the charges Signup and view all the answers

What describes the interaction between a plastic rod rubbed with paper and a glass rod rubbed with silk?

The two rods attract each other. Signup and view all the answers

What is the result of rubbing two objects of the same material against each other?

Neither object becomes charged. Signup and view all the answers

What is the main characteristic of unlike charges?

They attract each other Signup and view all the answers

Which type of charged object behaves like a polythene rod?

Negatively charged objects. Signup and view all the answers

What occurs to the charges on the metal sphere when the glass rod is removed?

The negative charge spreads over its surface Signup and view all the answers

What phenomenon can be attributed to static electricity?

Attraction and repulsion of charged objects. Signup and view all the answers

What happens when a piece of paper is rubbed with a plastic rod?

The paper becomes negatively charged. Signup and view all the answers

What type of electric state corresponds to charged glass in the experiments?

Positively charged. Signup and view all the answers

What term describes materials that allow charge to spread through them?

Conductors Signup and view all the answers

When a glass rod is rubbed against a metal rod, what charge does the metal rod acquire?

Positive charge Signup and view all the answers

Which of the following materials is classified as an insulator in the context of charge distribution?

Glass Signup and view all the answers

In the experiment with a positively charged rod and a suspended metal-coated ball, what is observed?

The ball repels the rod. Signup and view all the answers

If a plastic rod is rubbed and brought near a metal-coated ball, what is the expected outcome?

The ball does not respond to the rod. Signup and view all the answers

What is the significance of the terms negative and positive in charge classification?

They are arbitrary designations with mathematical meaning. Signup and view all the answers

What is the result when a charged metallic rod touches a large metal sphere on an insulating handle?

The metal ball comes closer but does not touch the rod. Signup and view all the answers

What is the typical charge acquired by a rubbed body?

$10^{-8}$ C Signup and view all the answers

Which statement correctly describes how charge spreads in a conductor?

Electrons can move anywhere within it. Signup and view all the answers

Which type of material has all electrons fixed in place?

Insulator Signup and view all the answers

What role do holes play in semiconductors?

They can move and cause conduction. Signup and view all the answers

What principle does a gold-leaf electroscope use to detect electric charge?

Repulsion of like charges Signup and view all the answers

What material is primarily used for the flexible strip in a gold-leaf electroscope?

Gold Signup and view all the answers

What occurs when a negatively charged polythene strip is brought near a negatively charged electroscope?

The gold leaf diverges further. Signup and view all the answers

What is the purpose of the Perspex insulator in a gold-leaf electroscope?

To prevent charge from leaking away Signup and view all the answers

What is the main purpose of an electrostatic paint spray gun?

To spread paint evenly and reduce waste Signup and view all the answers

How does the electrostatic paint spray gun charge paint particles?

By utilizing a fine ionizing electrode Signup and view all the answers

What happens to the powder particles that do not stick to the ridges of a fingerprint in fingerprint revealing?

They lose their positive charge and acquire a negative charge Signup and view all the answers

What role does grounding play in an electrostatic paint spray gun?

It allows charged particles to leak back into the power supply Signup and view all the answers

What is a common use of charged powder aside from revealing fingerprints?

Transferring toner onto paper in photocopy machines Signup and view all the answers

How does an electrostatic precipitator remove smoke and dust particles?

By repelling charged dust particles to earthed plates Signup and view all the answers

Which component in the electrostatic paint spray gun helps establish a circuit?

The grounding surface Signup and view all the answers

Why is the electrostatic paint spray gun not suitable for all kinds of paint?

Some paints do not conduct electricity Signup and view all the answers

Study Notes

Overview of Physics and Electricity

Science constructs theories and models for predicting natural phenomena through observations.
Electricity exists naturally and can manifest as static electricity or lightning.
Electrostatics studies electric charges when they are at rest.

Electrostatic Experiments with Glass and Plastic

Rubbing glass rods with silk alters their properties, creating electric charge.
Untouched glass rods do not interact; charged rods repel each other.
Rubbing plastic rods with paper or wool also leads to repulsion.
Plastic and glass rods exhibit attractive forces when rubbed with paper and silk, respectively.
Objects need to be of different materials to become charged through friction.

Classification of Charges

Charged objects are either positively (similar to glass) or negatively (similar to plastic) charged.
Like charges repel; unlike charges attract.
Common knowledge: Polythene becomes negatively charged; Perspex acetate becomes positively charged.

Charging Methods

Charging by contact: A negatively charged rod can impart its charge to a nearby uncharged object, causing repulsion after contact.
Conductors allow charge to move freely, while insulators do not facilitate charge transfer.

Induction and Earthing

During induction, a positively charged object can induce a separation of charges in a nearby uncharged conductor.
If the conductor is earthed while in the presence of the charged object, negative charges can be added, leaving the conductor negatively charged.

Concept of Opposite Charges

Oppositely charged objects neutralize when brought into contact.
Electrostatic force varies inversely with the square of the distance between charges; typical charge acquired through rubbing is 10^-8 C, whereas a lightning bolt can transfer up to 20 C.

Conductors vs Insulators

Conductors permit movement of charge (e.g., metals), whereas insulators do not allow charge movement (e.g., plastics).
Conducting liquids allow both positive and negative charge movement, while semiconductors can conduct through vacancies (holes).

Gold-leaf Electroscope

A gold-leaf electroscope detects electric state utilizing charge repulsion principles.
The divergence of the gold leaf indicates a charge's presence and its sign.
Charges can be tested using the electroscope by observing the interaction with various charged objects.

Applications of Electrostatics

Electrostatic Paint Spray Gun: Charges paint particles negatively, attracting them to a grounded surface for an even coat, minimizing waste.
Revealing Fingerprints: Charged powders bind to fingerprint ridges due to differences in charge.
Electrostatic Precipitator: Removes particles from factory emissions by using a charged grid that attracts dust to earthed plates, cleaning waste gases before release.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Explore the foundational concepts in Chapter 2 of Physics, where the activity of science is highlighted through the building of theories and models. This chapter explains how observations of natural phenomena lead to predictions about behavior in nature, focusing particularly on electricity. Test your understanding and interpretation of these ideas in this quiz.