Y10 Physics - Static Electricity (27)

What is static electricity?

the build-up of electric charge on the surface of an object due to the transfer of electrons.

What does earthing not work on

Insulators

How does electric shock form

Large amounts of potential

Electric field

Region around ä charged object where another charged object experiences electrostatic force

How is static charge produced by friction?

Electrons are transferred between two insulating materials when they are rubbed together.

Which particles are transferred when objects become charged?

Electrons are transferred

What happens when an object gains electrons?

It becomes negatively charged.

What happens when an object loses electrons?

It becomes positively charged.

What happens between like charges?

They repel each other.

What happens between opposite charges?

They attract each other.

What is an insulator?

A material in which electrons cannot move freely.

What is a conductor?

A material in which electrons can move freely.

Why does static charge build up on insulators?

Electrons cannot move freely through the material, so charge remains localised.

What is earthing?

Connecting an object to Earth so excess charge can flow away.

What is an electric field?

A region where a charged object experiences electrostatic force.

What happens to the electric field around a charged object as charge increases?

The electric field becomes stronger.

What is potential difference (p.d.)?

The energy transferred per unit charge between two points.

How can a large potential difference cause a spark?

A large p.d. creates a strong electric field that can ionise air, allowing charge to flow across the gap as a spark.

Polyethene rod

Electrons move to the rod

Acetate rod

Electrons move from the rod

Why is air normally an insulator?

Its electrons are not normally free to move through the air.

What happens when air becomes ionised?

Electrons are freed from atoms or molecules, allowing charge to flow and making the air conductive.

Why can static electricity be dangerous near flammable substances?

A spark can ignite flammable gases or vapours.

Why does a charged balloon stick to a wall?

The balloon causes charges in the wall to redistribute, producing an attractive electrostatic force.

How does electrostatic paint spraying work?

Paint droplets are given the same charge, so they repel each other and spread out; the object being painted is oppositely charged or earthed, (electrostatic induction)attracting the droplets.

Advantages pf electrostatic paint spraying

Even finish (like charges repel), reduction in paint waste (electrostatic force attraction), wrap around effect (field lines curve around target)

How does electrostatic crop sprayingl work?

Mist spraying crops is charged, and the plants are earthed, meaning electrostatic induction and then attraction

How does a photocopier use static electricity?

Static charge is used to attract toner particles to the correct areas before transferring them onto paper.

What is the unit of electric charge?

The coulomb (C).

What is the charge of an electron?

−1.6 × 10⁻¹⁹ C