Introduction to static electricity

邊玩邊學

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課程筆記

Atomic Structure and Charge

All matter is made of atoms and molecules.
Atoms have a nucleus containing protons (positive) and neutrons (neutral).
Electrons (negative) orbit the nucleus.
Atoms are neutral because they have equal numbers of protons and electrons.
If an atom loses or gains an electron, it becomes an ion (charged atom).
Losing an electron gives a positive ion; gaining an electron gives a negative ion.

How Objects Gain Static Charge

Static charge builds up when two objects rub against each other (friction).
Friction causes electrons to transfer from one object to the other.
The object that loses electrons becomes positively charged.
The object that gains electrons becomes negatively charged.
Only electrons move; protons stay in the nucleus.

Electrostatic Forces

Charged objects exert electrostatic forces on each other.
These forces are non-contact (they act without touching).
Like charges repel (positive-positive or negative-negative).
Unlike charges attract (positive-negative).

Examples of Static Electricity

Rubbing a balloon on hair transfers electrons from hair to balloon.
The balloon becomes negatively charged; the hair becomes positively charged.
The balloon then attracts the hair because opposite charges attract.
Two negatively charged balloons repel each other.
A Van de Graaff generator builds up a large static charge.
If a person touches it (insulated), their hairs gain the same charge and repel, standing on end.

Bohr model of a sodium atom showing nucleus (protons and neutrons) and electron shells.

Particle arrangement in solids, liquids, and gases.

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練習題

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1.What are the two particles that make up the nucleus of an atom?
Easy
- AProtons and neutrons
- BProtons and electrons
- CNeutrons and electrons
- DProtons, neutrons, and electrons
2.Which particle orbits around the nucleus and has a negative charge?
Easy
- AProton
- BNeutron
- CElectron
- DIon
3.Are electrostatic forces contact or non-contact forces?
Easy
- AContact forces
- BNon-contact forces
- CBoth contact and non-contact
- DNeither
4.What is the name for an atom that has lost or gained an electron?
Easy
- AIsotope
- BMolecule
- CIon
- DProton
5.Why do atoms usually have no overall charge?
Easy
- AThey have equal numbers of protons and electrons
- BThey have equal numbers of protons and neutrons
- CThey have more protons than electrons
- DThey have more electrons than protons
6.Which statement is true?
Easy
- AA positive charge attracts a negative charge
- BA positive charge attracts a positive charge
- CA negative charge attracts a negative charge
- DLike charges attract
7.Which statement is true about electrostatic charging?
Easy
- AProtons are transferred from one object to another
- BElectrons are transferred from one object to another
- CNeutrons are transferred from one object to another
- DBoth protons and electrons are transferred
8.A balloon is rubbed against a jumper and becomes negatively charged. What charge does the jumper become?
Medium
- ANegative
- BPositive
- CNeutral
- DIt depends on the material

更多題目

9.Someone drags their feet on a carpet and then gets a shock when touching a metal door handle. Which best explains why?
Medium
- AElectrons build up on the person, then jump to the metal handle
- BProtons build up on the person, then jump to the metal handle
- CThe metal handle becomes positively charged and attracts electrons from the person
- DThe carpet becomes positively charged and repels electrons from the person
10.If two negatively charged balloons are brought near each other, they will:
Easy
- AAttract each other
- BRepel each other
- CHave no effect
- DBecome neutral
11.A Van de Graaff generator causes a person's hair to stand up. Why does this happen?
Medium
- AEach hair becomes negatively charged and they attract each other
- BEach hair becomes positively charged and they repel each other
- CAll hairs have the same charge and repel each other
- DAll hairs have opposite charges and attract each other
12.An object becomes positively charged. Which process occurred?
Easy
- AIt gained protons
- BIt lost electrons
- CIt gained neutrons
- DIt lost protons
13.A student rubs a plastic rod with a cloth. The rod becomes negatively charged. Which statement explains this?
Medium
- AProtons move from the cloth to the rod.
- BElectrons move from the cloth to the rod.
- CProtons move from the rod to the cloth.
- DElectrons move from the rod to the cloth.
14.A student uses a Van de Graaff generator to charge a metal dome. She touches the dome and her hair stands on end. Why does her hair stand on end?
Medium
- AHer hair gains opposite charges, which attract.
- BHer hair becomes negatively charged and is attracted to the dome.
- CEach strand of hair gains the same charge, so they repel each other.
- DThe dome repels her hair because they have opposite charges.
15.A teacher rubs a balloon on her hair. The balloon becomes negatively charged. What charge does her hair become?
Easy
- APositive
- BNegative
- CNeutral
- DBoth positive and negative
16.A student holds a positively charged rod near a stream of water from a tap. The water stream bends towards the rod. Which explanation is correct?
Medium
- AThe water molecules are polar and the positive rod attracts the negative end of the water molecules.
- BThe water becomes positively charged and is attracted to the rod.
- CThe rod repels the water because both have the same charge.
- DThe water is neutral and cannot be affected by the rod.
17.A student has two metal spheres on insulating stands. Sphere A has a charge of +4 nC and sphere B has a charge of -2 nC. They are brought into contact and then separated. What is the charge on each sphere after separation?
Hard
- AA = +1 nC, B = +1 nC
- BA = +2 nC, B = 0 nC
- CA = +3 nC, B = -1 nC
- DA = +4 nC, B = -2 nC
18.A student investigates static electricity using a gold-leaf electroscope. She charges the electroscope negatively. She then brings a positively charged rod near the top plate without touching it. What happens to the gold leaf?
Hard
- AIt rises further because more negative charge is induced on the leaf.
- BIt falls because positive charge from the rod neutralizes the leaf.
- CIt rises because the rod attracts the leaf.
- DIt falls because electrons are repelled from the plate to the leaf, reducing the leaf's charge.
19.In a factory, a machine uses static electricity to paint metal objects. The paint droplets are given a negative charge, and the metal object is given a positive charge. Why does this make the paint spread evenly?
Medium
- AThe paint droplets repel each other and are attracted to the object.
- BThe paint droplets are attracted to each other and to the object.
- CThe object repels the paint droplets, causing them to spread.
- DThe paint droplets become neutral and stick to the object.
20.A student rubs a polythene rod with a duster. The rod becomes negatively charged. The student then brings the rod near a small piece of paper. The paper is attracted to the rod. Why is the paper attracted?
Medium
- AThe paper is positively charged.
- BThe rod induces an opposite charge on the paper, causing attraction.
- CThe paper becomes negatively charged by contact.
- DThe rod and paper have the same charge.
21.Which particle is transferred when an object becomes charged by friction?
Easy
- AProton
- BNeutron
- CElectron
- DIon
22.A student sets up two balloons on strings. Balloon X is negatively charged. When balloon Y is brought near, they repel each other. What can you conclude about balloon Y?
Medium
- AIt is positively charged.
- BIt is negatively charged.
- CIt is neutral.
- DIt could be either positively charged or neutral.
23.What is the name given to an atom that has lost or gained electrons?
Easy
- AIsotope
- BIon
- CMolecule
- DCompound
24.Which of the following is a non-contact force?
Easy
- AFriction
- BAir resistance
- CElectrostatic force
- DTension
25.A student uses a Van de Graaff generator to charge a metal dome. The dome becomes positively charged. The student then touches the dome while standing on an insulating mat. Which of the following best explains why the student's hair stands on end?
Medium
- AEach hair gains the same positive charge, causing them to repel each other.
- BEach hair gains a negative charge, causing them to repel each other.
- CThe hair becomes neutral and is attracted to the dome.
- DThe hair loses electrons and becomes negatively charged.
26.A student rubs a polythene rod with a cloth. The rod becomes negatively charged. Which statement correctly describes the transfer of charge?
Medium
- AElectrons move from the cloth to the rod.
- BProtons move from the cloth to the rod.
- CElectrons move from the rod to the cloth.
- DProtons move from the rod to the cloth.
27.What is the name given to an atom that has gained or lost electrons?
Easy
- AIon
- BIsotope
- CMolecule
- DNeutron
28.A student brings a negatively charged balloon near a small piece of paper. The paper is attracted to the balloon. Which is the best explanation?
Medium
- AThe balloon induces a positive charge on the near side of the paper, causing attraction.
- BThe paper is positively charged.
- CThe balloon transfers electrons to the paper, making it negatively charged and then repelling it.
- DThe paper is neutral and cannot be attracted to a charged object.
29.In a factory, paint droplets are given a negative charge and the metal object to be painted is given a positive charge. Which statement explains why this method produces an even coat of paint?
Medium
- AThe negatively charged droplets repel each other and are attracted to the positively charged object.
- BThe negatively charged droplets attract each other and spread out evenly on the object.
- CThe positively charged object repels the droplets, causing them to spread out.
- DThe droplets are neutral and stick to the object by adhesion.
30.A negatively charged rod is brought near the cap of a gold-leaf electroscope without touching it. The gold leaves diverge. What charge is induced on the leaves?
Medium
- ANegative
- BPositive
- CNeutral
- DNo charge is induced
31.Two metal spheres on insulating stands are brought into contact. Sphere A has a charge of +6 nC and sphere B has a charge of -2 nC. After separation, what is the charge on each sphere?
Hard
- A+2 nC on each sphere
- B+4 nC on A, 0 nC on B
- C+6 nC on A, -2 nC on B
- D+2 nC on A, +2 nC on B
32.A student rubs a plastic rod with a cloth and then holds it near a stream of water from a tap. The water stream bends towards the rod. Which of the following is the most likely explanation?
Medium
- AThe rod induces an opposite charge in the water, causing attraction.
- BThe rod repels the water because both are negatively charged.
- CThe water is positively charged and attracts the rod.
- DThe rod heats the water, causing it to expand and bend.
33.What particles are transferred when an object becomes charged by friction?
Easy
- AElectrons
- BProtons
- CNeutrons
- DIons
34.A student has two balloons on strings. Balloon X is positively charged. When balloon Y is brought near, they attract each other. What can you conclude about balloon Y?
Medium
- ABalloon Y is negatively charged or neutral.
- BBalloon Y is positively charged.
- CBalloon Y is negatively charged only.
- DBalloon Y is neutral only.
35.A student investigates static electricity using a gold-leaf electroscope. The electroscope is given a positive charge. A negatively charged rod is brought near the cap without touching. What happens to the gold leaves?
Hard
- AThey diverge more.
- BThey collapse.
- CThey remain unchanged.
- DThey move together and then apart.
36.Which two particles make up the nucleus of an atom?
Easy
- AProtons and neutrons
- BProtons and electrons
- CNeutrons and electrons
- DProtons, neutrons and electrons
37.A student rubs a balloon on their hair. The balloon becomes negatively charged. What happens to the hair?
Medium
- AIt becomes positively charged and is attracted to the balloon.
- BIt becomes negatively charged and is attracted to the balloon.
- CIt becomes positively charged and is repelled by the balloon.
- DIt remains neutral and is attracted to the balloon.
38.A student uses a Van de Graaff generator to charge a metal dome. The dome becomes positively charged. A person standing on an insulating stool touches the dome. Which statement explains why the person's hair stands on end?
Hard
- AThe hair gains electrons from the dome and becomes negatively charged, causing repulsion between hairs.
- BThe hair loses electrons to the dome and becomes positively charged, causing repulsion between hairs.
- CThe hair becomes neutral and is repelled by the dome.
- DThe hair gains protons from the dome and becomes positively charged, causing attraction between hairs.
39.A student has two balloons on strings. Balloon X is negatively charged. When balloon Y is brought near, they attract each other. What can you conclude about balloon Y?
Medium
- ABalloon Y must be positively charged.
- BBalloon Y must be negatively charged.
- CBalloon Y could be positively charged or neutral.
- DBalloon Y could be negatively charged or neutral.
40.In a factory, a machine uses static electricity to paint metal objects. The paint droplets are given a negative charge, and the metal object is given a positive charge. Which statement explains why this method is efficient?
Medium
- AThe paint droplets repel each other, spreading out evenly, and are attracted to the object.
- BThe paint droplets are attracted to each other, forming larger drops that stick to the object.
- CThe paint droplets are repelled by the object, so they bounce off and coat the surface evenly.
- DThe paint droplets become neutral when they hit the object, ensuring a thick coat.
41.A positive charge attracts a negative charge.
Easy
True or false?
42.A negative charge attracts a negative charge.
Easy
True or false?
43.For an object to become charged, protons are transferred from one object to another.
Easy
True or false?
44.Which of the following best describes electrostatic forces?
Easy
- AContact forces that require objects to touch
- BNon-contact forces that act at a distance
- CForces that only attract
- DForces that only repel
45.Select all the statements that are true about electrostatic charging. (Select all that apply)
Medium
- ALike charges repel each other.
- BUnlike charges attract each other.
- CElectrostatic forces are contact forces.
- DElectrons are transferred when an object becomes charged by friction.
- EProtons are transferred when an object becomes charged by friction.
46.Match each particle to its charge.
Easy
- Proton
- Neutron
- Electron
- Positive
- Negative
- Neutral
47.Arrange the following steps in the correct order to describe how a balloon becomes negatively charged when rubbed against hair.
Medium
- The balloon gains electrons from the hair.
- The balloon becomes negatively charged.
- The hair loses electrons.
- The balloon is rubbed against the hair.
48.A student rubs a plastic rod with a cloth. The rod becomes negatively charged. Which particle is transferred and in which direction?
Medium
- AProtons move from cloth to rod
- BElectrons move from cloth to rod
- CProtons move from rod to cloth
- DElectrons move from rod to cloth
49.A student brings a negatively charged rod near a metal sphere on an insulating stand without touching it. The sphere is initially neutral. Which of the following occur? (Select all that apply)
Hard
- AElectrons in the sphere are repelled away from the rod
- BThe sphere becomes permanently negatively charged
- CThe side of the sphere nearest the rod becomes positively charged
- DThe sphere becomes positively charged overall
- EThe sphere remains neutral overall
50.Electrostatic forces can act between objects that are not touching.
Easy
True or false?
51.Complete the sentence.
Easy
The two particles that make up the nucleus are ____ and ____.
52.Explain why atoms usually have no overall charge.
Medium
53.Describe how an object gains a static charge.
Medium
54.Complete the sentences about static electricity.
Easy
An atom that has lost or gained an electron is called an ____. The process of losing or gaining electrons is called ____.
55.A metal sphere has a charge of +8 nC. It is touched to an identical neutral metal sphere and then separated. What is the charge on each sphere after separation? (Answer in nC)
Medium
56.A neutral metal sphere gains 3.2 × 10⁶ electrons. What is its charge in coulombs? (Charge of one electron = 1.6 × 10^-19 C)
Hard
57.Explain why a person's hair stands on end when they touch a charged Van de Graaff generator.
Medium
58.A metal sphere has a charge of +8 nC. It is touched to an identical neutral metal sphere and then separated. What is the charge on each sphere after separation? (Answer in nC)
Medium
- A3 nC
- B4 nC
- C5 nC
- D6 nC
59.A neutral metal sphere gains 3.2 × 10⁶ electrons. What is its charge in coulombs? (Charge of one electron = 1.6 × 10^-19 C)
Hard
- A1 C
- B2 C
- C-1 C
- D-5.12e-13 C

複習筆記

## Static Electricity Revision Notes - **Atoms** have a nucleus (protons + neutrons) and orbiting electrons. - **Protons** are positive (+), **electrons** are negative (-), **neutrons** are neutral. - Atoms are neutral because they have equal numbers of protons and electrons. - **Ionisation**: losing or gaining electrons turns an atom into an **ion** (charged atom). - **Static charge** builds up when two objects rub together: friction transfers electrons from one to the other. - **Electrostatic forces** are **non-contact** forces between charged objects. - **Like charges repel, unlike charges attract.** - Example: Rubbing a balloon on hair transfers electrons from hair to balloon. Balloon becomes negative, hair positive → they attract. - Two negatively charged balloons repel each other. - **Van de Graaff generator** builds up large static charge. Touching it (while insulated) gives you a charge; all your hairs gain the same charge and repel, making them stand up. ### Key Points to Remember - Only **electrons** move during charging, not protons. - Charging by friction: one object loses electrons (becomes positive), the other gains electrons (becomes negative). - Electrostatic forces can attract or repel without contact.

Nucleus: The central part of an atom, containing protons and neutrons.
Proton: A positively charged particle in the nucleus.
Electron: A negatively charged particle that orbits the nucleus.
Neutron: A neutral particle (no charge) in the nucleus.
Ion: An atom that has lost or gained electrons, becoming charged.
Ionisation: The process of an atom losing or gaining electrons.
Static charge: An electric charge that builds up on an object, often by friction.
Electrostatic force: A non-contact force between charged objects.
Like charges repel, unlike charges attract: The rule describing how charged objects interact: same charges push apart, opposite charges pull together.
Van de Graaff generator: A device that builds up large static charges; touching it can make hair stand up due to repulsion of like charges.

字卡

What are the two particles that make up the nucleus of an atom?

Protons and neutrons.

What particle orbits the nucleus and what charge does it have?

Electrons, which are negatively charged.

What charge do protons have?

Protons are positively charged.

What charge do neutrons have?

Neutrons are neutral (no charge).

Why are atoms normally neutral?

Because they have equal numbers of protons and electrons.

What is an ion?

An atom that has lost or gained an electron.

What is ionisation?

The process of an atom losing or gaining electrons.

How does an object gain a static charge?

By rubbing against another object. Friction causes one object to lose electrons and the other to gain electrons.

What type of force is electrostatic force?

Non-contact force.

What does 'like charges repel, unlike charges attract' mean?

Two objects with the same charge push apart; two objects with opposite charges pull together.

When a balloon is rubbed against hair, what happens to electrons?

Electrons transfer from the hair onto the balloon.

After rubbing a balloon on hair, what charges do the balloon and hair have?

The balloon becomes negatively charged, and the hair becomes positively charged.

Why does a charged balloon attract hair?

Because the balloon and hair have opposite charges (unlike charges attract).

What happens when two negatively charged balloons are placed near each other?

They repel each other because they have the same charge (like charges repel).

What is a Van de Graaff generator?

A device that builds up large static charges, similar to rubbing a balloon.

Why do a person's hairs stand up when they touch a Van de Graaff generator?

All hairs gain the same charge, so they repel each other and spread out.

True or false: A positive charge attracts a negative charge.

True.

True or false: A negative charge attracts a negative charge.

False. Like charges repel.

True or false: For an object to become charged, protons are transferred from one object to another.

False. Electrons are transferred, not protons.

A balloon rubbed against a jumper becomes negatively charged. What charge does the jumper get?

The jumper becomes positively charged because it loses electrons to the balloon.

Why might you get an electric shock after dragging your feet on a carpet and touching a metal door handle?

Friction causes a build-up of static charge on your body. When you touch the metal handle, the charge discharges, causing a shock.

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