Physics: Static Electricity and Electrostatics

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Questions and Answers

What phenomenon describes the buildup of stationary electrical charge on a material's surface, typically resulting from friction?

  • Current Electricity
  • Quantum Entanglement
  • Electromagnetic Induction
  • Static Electricity (correct)

When a plastic ruler is rubbed with a cloth, it can pick up small pieces of paper. What is the fundamental reason for this?

  • The ruler changes its mass.
  • The ruler becomes magnetized.
  • The ruler gains an electric charge. (correct)
  • The ruler creates a gravitational field.

An atom is considered electrically neutral when which condition is met?

  • It has more neutrons than protons.
  • It has more electrons than protons.
  • It has an equal number of protons and neutrons.
  • It has an equal number of protons and electrons. (correct)

What is the overall charge of an object that has more electrons than protons?

<p>Negative (A)</p> Signup and view all the answers

An object becomes positively charged when it loses electrons. Which statement best portrays the movement of electrons?

<p>Electrons are transferred from the object. (D)</p> Signup and view all the answers

A glass rod becomes positively charged when rubbed with silk. What happens to the silk during this process?

<p>It gains electrons and becomes negatively charged. (A)</p> Signup and view all the answers

According to the concept of electro-negativity, which material is more likely to donate electrons when rubbed against another material?

<p>Glass (D)</p> Signup and view all the answers

When two materials are rubbed together, and static electricity is generated, what is actually occurring at the atomic level?

<p>Transfer of electrons from one material to the other (D)</p> Signup and view all the answers

If a balloon becomes negatively charged after being rubbed on a wool sweater, what charge does the wool sweater have?

<p>Positive (A)</p> Signup and view all the answers

Why can insulators easily be charged by friction compared to conductors?

<p>Insulators prevent electrons from escaping easily. (D)</p> Signup and view all the answers

Which of the following materials will most likely retain a static charge when rubbed?

<p>Glass rod (D)</p> Signup and view all the answers

Which statement best describes why conductors cannot easily be charged by friction?

<p>Excess electrons quickly flow away. (C)</p> Signup and view all the answers

In electrostatic induction, what happens when a negatively charged rod is brought near, but not touching, a neutral metal can?

<p>Electrons in the can move away from the rod. (B)</p> Signup and view all the answers

When a charged rod is brought close to a neutral piece of paper, the paper is attracted to the rod. What occurs at the molecular level within the paper to cause this attraction?

<p>The paper molecules align with the charged rod. (B)</p> Signup and view all the answers

Why are static charge effects typically more noticeable on dry days compared to humid days?

<p>Humidity increases the conductivity of the air, neutralizing charges faster. (D)</p> Signup and view all the answers

What is the phenomenon of static discharge?

<p>A sudden flow of electric charge between two objects. (D)</p> Signup and view all the answers

What is the relationship between conductors and insulators in terms of electron flow?

<p>Conductors allow electrons to flow freely, while insulators do not. (B)</p> Signup and view all the answers

If a conductor and an insulator both have extra electrons placed on them, how will the distribution of electrons differ over time?

<p>Electrons will spread out evenly on the conductor but remain concentrated on the insulator. (D)</p> Signup and view all the answers

Where do excess positive charges tend to distribute themselves on a conductive object?

<p>Concentrated on the surface of the conductor. (B)</p> Signup and view all the answers

Two balloons are rubbed with a woolen cloth, giving them a static charge. If the balloons are then hung next to each other, what will happen?

<p>They will repel each other. (C)</p> Signup and view all the answers

In industrial smokestacks, how is static electricity used to reduce air pollution?

<p>By charging smoke particles and then attracting them to oppositely charged plates. (B)</p> Signup and view all the answers

Ian uses a plastic comb on a dry day to comb his hair. His hair is attracted to the comb. On a humid day, this effect is reduced. Why?

<p>The moisture in the air allows the charge to dissipate more quickly. (A)</p> Signup and view all the answers

Commercial airplanes can build up a significant static charge when flying at high altitudes due to friction with air. How does the charge distribute itself on the airplane's metallic skin?

<p>The charge is more concentrated at pointy or curved areas. (B)</p> Signup and view all the answers

In electrostatic painting, what role does static electricity play in enhancing the painting process?

<p>It helps to uniformly attract the paint particles to the object. (D)</p> Signup and view all the answers

During lightning storms, what process leads to the buildup of electrical charge in storm clouds?

<p>Friction between particles (D)</p> Signup and view all the answers

Which of the following is NOT a common application of static electricity?

<p>Induction furnaces (C)</p> Signup and view all the answers

How do air filters that use static electricity work to remove dust and particles?

<p>They use static electricity to attract and trap charged particles. (B)</p> Signup and view all the answers

Consider an object with a uniform distribution of positive charge. If this object is brought near a neutral conductor, what will occur within the conductor due to induction?

<p>Negative charges will accumulate on the side of the conductor nearest the charged object. (C)</p> Signup and view all the answers

A rubber rod is rubbed with fur, giving the rubber rod a negative charge. What can be inferred about the fur after this interaction?

<p>The fur is positively charged. (D)</p> Signup and view all the answers

A metal sphere is charged by induction using a positively charged rod. Which of the following accurately describes the process?

<p>Electrons redistribute within the sphere due to the presence of the rod. (B)</p> Signup and view all the answers

Why is it generally safer to be inside a car during a lightning storm?

<p>The metal body of the car acts as a Faraday cage, conducting the charge around the occupants. (D)</p> Signup and view all the answers

Which factor has the greatest influence on whether a material will act as a conductor or an insulator?

<p>The availability of free electrons within the material (C)</p> Signup and view all the answers

If a neutral metal object is touched by a positively charged object, what will happen to the metal object, assuming it is then isolated?

<p>It will become positively charged. (A)</p> Signup and view all the answers

In the context of static electricity, what is meant by 'grounding' an object?

<p>Connecting the object to a large reservoir of charge, like the Earth. (A)</p> Signup and view all the answers

Assume you have two identical metal spheres. Sphere A has a charge of +4q, and Sphere B has a charge of -2q. If the spheres are brought into contact and then separated, what will be the charge on each sphere?

<p>Sphere A: +q, Sphere B: +q (B)</p> Signup and view all the answers

Why are computer components typically packaged in antistatic bags?

<p>To protect them from electrostatic discharge. (D)</p> Signup and view all the answers

What is the primary reason for charge accumulation at points on a charged conductor?

<p>Greater repulsive force between charges at those points (A)</p> Signup and view all the answers

Consider a scenario where a neutral, conducting sphere is grounded while a positively charged rod is brought near but not touching it. What will be the charge on the sphere after the ground connection is broken and the rod is removed?

<p>Negative (C)</p> Signup and view all the answers

How does the presence of sharp points on a charged object influence the electric field around the object?

<p>It concentrates the electric field at those points. (C)</p> Signup and view all the answers

Flashcards

What is static electricity?

Static electricity is the buildup of stationary electrical charge on a material's surface, often via friction.

Electric Charge Example

After being rubbed, a plastic ruler can attract paper scraps, showing it carries electric charge.

What is electrostatics?

The interaction between static electric charges.

What are atoms composed of?

Matter is composed of atoms, which contain protons (positive charge), neutrons (neutral), and electrons (negative charge).

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Charge and Electrons

If electrons equal protons, the charge is neutral. More electrons result in a negative charge, fewer electrons in a positive charge.

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Electro-negativity

Arranges materials by their ability to donate or accept electrons; glass donates, Teflon accepts.

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Electron Transfer

Rubbing transfers electrons, not creates. One material loses electrons to another material.

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Rubbing a balloon

Involves a transfer of electrons from one material to another to create charged objects.

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What are insulators?

Materials that inhibit electron flow, allowing easy static charging. Examples: glass, wood, rubber, plastic

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What are conductors?

Materials that allow electrons to flow freely so cannot hold static charge. Examples: copper, iron, nickel, aluminium.

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What is electrical induction?

Charge production in an uncharged body by bringing a charged object close.

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Static Discharge

Static discharge occurs when a buildup of electrons flows, like exceeding 20,000 volts from scuffing shoes.

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How do conductors work?

Electrons flow freely; conductors used to ground charge.

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Charges: surface or inside?

Electrons cluster to maximize distance given mutual repulsion if object has the same or similar charge when ungrounded. Result is excess of charge at surface.

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What causes lightning?

Lightning is electrical discharge due to friction in clouds building charge.

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Static electricity applications

Electrostatic dusters, printers, copiers, painting, and air filters all take advantage of static electricity.

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Study Notes

  • Physics 1.3 focuses on demonstrating an understanding of electricity and magnetism.
  • It's an externally assessed standard worth 4 credits.

Static Electricity

  • Static electricity involves a stationary electrical charge buildup on a material's surface, often through friction.

Electrostatics

  • Rubbing a plastic ruler can cause it to carry an electric charge and attract paper scraps.
  • Charging by friction involves the transfer of charge through rubbing.
  • Electrostatics studies the interaction between static electric charges.

Origin of Charges

  • Matter comprises atoms, which include protons (positive charge), neutrons (neutral), and electrons (negative charge).
  • Atoms are comprised of a positively charged nucleus and negative electrons
  • An atom is neutral if it has an equal number of electrons and protons.
  • An atom has a negative charge if it gains electrons.
  • An atom has a positive charge if it loses electrons.
  • Rubbing materials doesn't create charge; it transfers electrons from one material to another.
  • When a balloon is rubbed with wool, electrons move from the wool to the balloon, creating a negative charge on the balloon and leaving a positive charge on the wool.

Electro-negativity

  • Electro-negativity ranks materials by their tendency to donate or accept electrons.
  • Materials like glass tend to donate electrons and teflon tends to accept electrons.

Insulators and Conductors

  • Insulators are materials that do not allow electrons to flow easily.
  • Examples of insulators are glass, wood, rubber, hair, and plastic.
  • Insulators can easily be charged by friction because extra electrons do not escape easily.
  • Conductors are materials that allow electrons to flow easily.
  • Examples of conductors are metals like copper, iron, nickel, and aluminum.
  • Conductors cannot easily be charged by friction because extra electrons escape easily.

Induction

  • Induction is the production of a charge in an uncharged body by bringing a charged object close.
  • When a negatively charged rod is brought near a metal can, the electrons in the can are pushed away from the rod.
  • A negatively charged rod near a metal can causes the top of the can to become positive and the bottom to become negative
  • In this induction setup, attraction is greater than repulsion.
  • Molecules of paper align when a charged rod is brought close to paper scraps
  • When a charged rod is brought close to paper scraps, there exists attraction between the rod and the + charge, which is greater than repulsion.

Static Discharge

  • Humans can't feel less than 2,000 volts of static discharge.
  • Static charge from scuffing shoes on a carpet can exceed 20,000 volts.
  • In a conductor, electrons can flow freely through it.
  • Charge builds up on the surface of an insulator.

Example Question 1

  • When two balloons are rubbed with a woolen cloth, the balloons' surfaces will either have electrons rubbed on or rubbed off, thus becoming charged.
  • Since the balloons contain the same charge, the balloons will repel each other, moving away from each other / push apart.

Example Question 2

  • Industrial pollution is reduced by giving smoke particles a negative charge as they enter a chimney.
  • Plates in the chimney are given a positive charge, which attracts the negatively charged particles and reduces pollution.

Example Question 3

  • Combing hair on a dry day charges the hair and comb due to friction, the charge stays on the hairs and the comb and so the attraction between them lasts for a long time.
  • On a damp day, the moisture in the air allows electrons to flow and the charge on both the hairs and the comb are quickly neutralised.
  • A metal comb is held which means any charge and the rubbing is quickly lost as electrons can flow, so hair is not attracted to a neutral comb.

Example Question 4

  • Rubbing between a plane and the air can cause the plane to become negatively charged.
  • Wing tips and tail will have a higher concentration of charge whereas the flat surfaces will have charges that are more evenly spread out.

Page 16 SciPad Questions

  • Electrostatic Painting involves the paint and the object having opposite charges.
  • Electrostatic painting is more efficient and produces a better finish than traditional painting methods.
  • During electrostatic painting, the object being painted must be a conductor of electricity.

Electrical Discharge through Air

  • Electrical discharge occurs when a build up of electrons flow through the air, like lightning.
  • Friction between particles in the clouds causes charge to build up.
  • When the charge is large enough, a bolt of lightning (a large electrical discharge) will form.
  • There are more than 50,000 lightning strikes per year in New Zealand, with one death reported every five to ten years.

Applications of Static Electricity

  • Static electricity is applied to electrostatic dusters, printers, photocopiers, painting, and air filters for dust removal.

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