State the rule for forces between charges.

Like charges repel; unlike charges attract.

What is an insulator?

A material in which charge cannot flow easily, such as polythene, glass or rubber.

A material containing free electrons, so charge flows through it easily, such as a metal.

Connecting an object to the ground with a conductor so charge flows away and the object becomes neutral.

How does a gold-leaf electroscope show that an object is charged?

The stem and leaf gain the same charge and repel, so the leaf rises.

Define an electric field.

A region where a charged object feels a force.

What do electric field lines show?

The direction of the force on a positive charge.

Describe the field lines around a negative point charge.

Straight lines pointing inwards, towards the charge.

What is the field like between two oppositely charged parallel plates?

Uniform: straight, parallel, evenly spaced lines from the positive plate to the negative plate.

Give two uses of static electricity.

Photocopiers and electrostatic paint spraying (also precipitators).

Why are fuel tankers earthed when refuelling aircraft?

To let charge flow away so no spark can ignite the fuel vapour.

What causes lightning?

A large build-up of charge in a cloud that discharges as a giant spark.

Static electricity and electric fieldsIB MYP Physics: Flashcards

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What is transferred when two insulators are rubbed together?

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What is transferred when two insulators are rubbed together?: Electrons only. Protons stay fixed in the nucleus.
What charge does an object get if it gains electrons?: Negative.
What charge does an object get if it loses electrons?: Positive.
State the rule for forces between charges.: Like charges repel; unlike charges attract.
What is an insulator?: A material in which charge cannot flow easily, such as polythene, glass or rubber.
What is a conductor?: A material containing free electrons, so charge flows through it easily, such as a metal.
What is earthing?: Connecting an object to the ground with a conductor so charge flows away and the object becomes neutral.
How does a gold-leaf electroscope show that an object is charged?: The stem and leaf gain the same charge and repel, so the leaf rises.
Define an electric field.: A region where a charged object feels a force.
What do electric field lines show?: The direction of the force on a positive charge.
Describe the field lines around a negative point charge.: Straight lines pointing inwards, towards the charge.
What is the field like between two oppositely charged parallel plates?: Uniform: straight, parallel, evenly spaced lines from the positive plate to the negative plate.
Give two uses of static electricity.: Photocopiers and electrostatic paint spraying (also precipitators).
Why are fuel tankers earthed when refuelling aircraft?: To let charge flow away so no spark can ignite the fuel vapour.
What causes lightning?: A large build-up of charge in a cloud that discharges as a giant spark.

Exam questions on Static electricity and electric fields

A student in a school laboratory rubs a dry polythene rod with a woollen cloth. Afterwards the rod is able to pick up small scraps of paper. Careful tests show that the rod has become negatively charged and the cloth has become positively charged.
Explain why the polythene rod becomes negatively charged when it is rubbed with the cloth.2 marks
At an airport, a fuel tanker pumps aviation fuel into an aircraft through a long rubber hose. As the fuel rushes through the hose, friction makes charge build up on the hose and the tanker. Before pumping begins, a thick metal cable is clipped from the tanker to the aircraft, and a second cable connects the aircraft to the ground.
Explain why a spark between the tanker and the aircraft would be dangerous if the cables were not used.2 marks
A group of students investigate how the number of times a polythene rod is rubbed with a woollen cloth affects the amount of charge the rod gains. After rubbing, they touch the rod to the metal cap of a gold-leaf electroscope and use a protractor to measure how far the gold leaf rises away from the metal stem. The electroscope is discharged by touching the cap before every trial.
Identify the independent variable, the dependent variable and one control variable in this investigation.3 marks

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Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).