(temp - edit with correct material) topic 11 statics

Which part of the atom can be removed easily?

Electrons (Through ionisation or friction)

Explain how friction between two different materials when they are rubbed together can lead to the transfer of electrons

the friction causes electrons to be stripped from one material and transferred to the other. The material that has lost electrons will be left with a positive charge; the material that has gained electrons will have an equal and opposite negative charge.

What happens if two similar charges are brought together? What about two opposite charges?

Like charges repel; unlike charges attract. 

Give examples of charging by conduction

Rubbing cloth on a rod, rubbing balloon on jumper, escalator handle building static charge, Van der Graaf generator

Give examples of charging by induction

Neutral dust particles sticking to screen, balloon sticking to wall, lightning, paper dots sticking to comb.

Explain the role of electron movement in receiving an electric shock after rubbing your feet on synthetic carpet

Friction caused electrons to be transferred to you give you a negative charge. You are shocked when touching a metal object as the electrons pass from you to the metal object to discharge you and flow to the ground.

Explain the role of electron movement in lightning striking a metal pylon.

Collisions of particles cause charge to separate and the bottom of the cloud to become negative. This repels electrons on the surface of the earth which move away. Inducing a positive charge at the surface. The electrons are attracted to the ground so pass from the cloud to the earth. The conducting metal pylon provides a lower resistance route to the earth than the air, so it strikes.

Explain the role of electron movement in a balloon sticking to the wall after being rubbed on a jumper

If the balloon is positive then it attracts electrons in the wall towards it, inducing a charge separation. The wall is overall neutral, but the side closest to the balloon has an excess negative charge, and the balloon will stick.

What is meant by the term “earthing”?

The transfer of excess charge to the earth, which behaves as an infinite reservoir of charge allowing an object to discharge.

Describe the use of static electricity in spray painting

The paint is passed through a charged grille and given the same charge. This makes the droplets repel each other, ensuring an even wider even coating. The object being painted has an opposite charge to the paint, and attracts the droplets

Describe the use of static electricity in pesticide sprays.

All droplets have the same charge so electrostatically repel creating a wider spray to reach a larger area. These droplets induce an opposite charge on the leaves, so they attract to the leaf creating an even spread.

Describe the use of static electricity in precipitators in chimneys

Smoke particles rising upwards through the chimney acquire a negative charge. They are then attracted to positively charged plates positioned above the grille, removing them from the gases being emitted into the atmosphere.

Describe the dangers of sparks when refuelling and suggest how this danger can be reduced

Any sparks could cause a fire/explosion if it ignites the fuel fumes. An earth wire connecting the fuelling pipe to the ground will remove any charge built up as the fuel passes through the pipe, reducing the risk of sparking

What is meant by the term “electric field”?

A region where a charged particle experiences an electrical force 

Which way do electric field lines always point?

They show the direction a positive test charge would move, It cannot move in two directions at once at a point so there must be a resultant of these two directions.

What does it mean if electric field lines are drawn closer together?

Lines drawn closer together represent a stronger field  

Describe the field between two parallel plates. Explain how you can tell from a diagram.

The field is uniform (the same everywhere) as the lines are equally spaced.

How does the concept of an electric field explain common electrostatic phenomena?

Charged objects experience a force in the presence of an electric field.