Staic Eletricity

Question 1

How can insulators be charged?

Answer 1

By friction between two insulators, through the transfer of electrons from one material to another.

Question 2

Charges of the materials gaining and losing electrons

Answer 2

G - negative

L - equal positive charge

Question 3

What does static electricity mean?

Answer 3

S - not moving

E - electrons moving

Question 4

Induction

Answer 4

Temporary creation of charge in a neutral object e.g. Charged balloon on a wall or charged comb picking up small pieces of paper.
Using a charged object to force charges in an uncharged object to move.

Question 5

Charged balloon being attracted to a wall

Answer 5

Due to induction. The negatively charged balloon (from gaining electrons from hair when rubbed) would stick to the neutral wall. This is because charges on the surface of the wall can move a little. The negative charges on the balloon repel the electrons on the wall (which move as they are are mobile), leaving behind a positive charge and therefore attraction.

Question 6

Nature of static charge

Answer 6

Same in size. Opposite in charge

Question 7

How to dissipate static electricity (earthing)

Answer 7

Connect it to the earth by a metal rod because it is a conductor. (Neg) charge/electrons flow down to earth. (Pos) electrons/charge flow up from the earth. Positive charges can’t move.

Question 8

Van de Graaf

Answer 8

Electrons are being transferred in static electricity so they are attracted…

Question 9

Tin foil cases flying in the air on a Van De Graaf

Answer 9

Conductors become negatively charged and repel

Question 10

Hair standing on ends when hands are placed on the Van de Graaf

Answer 10

They repel due to negative charges. Hair is light compared to the force of gravity so they stand on end. An insulating plastic box is used to stop connection to earth

Question 11

Earthing

Answer 11

Removes excess charge by movement of electrons as the electrons are conducted/move down to the earth. Metal is a conductor so it conducts the electrons to the ground meaning no sparks ignite an explosion and no shock is created.

Provides an easy route for static charges to travel to the ground so no charge can build up.

Question 12

Uses: spray paints and insecticides

Answer 12

Like charges repel so the spray is wider and covers a larger area. Static drops spread evenly as they all have the same charge and are attracted to the earth. The spray gun is positively charged which chases the paint particles to become positively charged. The object painted is negative which attracts the paint particles so less paint is wasted and there is an even coat.

Question 13

Other uses of static electricity

Answer 13

Laser printers, photocopiers, defibrillators, dust precipitators

Question 14

Photocopiers

Answer 14

Paper put through. Image projected onto positively charged copying plate. Where light falls on plate, electrical charges leaks away. Negatively charged toner particles are attracted to the remaining positive areas. Paper is placed on top and the toner is transferred

Question 14

Dust precipitators

Answer 14

Remove particles from waste gases in fossil fuel combustion. Smoke passes through a negative grid and the particles pick up negative charge. Attracted to collecting plate. Knocked to remove particles

Question 16

Defibrillators

Answer 16

Insulating handles. High voltage. Makes patients heart contract to keep pumping blood

Question 17

Dangers of sparking (fuelling cars)

Answer 17

Fuel running along a plastic or rubber pipe can cause friction and build up a static charge as they are both insulators. Therefore a spark can ignite fuels. This is dangerous because fuels are flammable and the spark can cause a fire or explosion

Question 18

Lightning (a flow of charge in the atmosphere)

Answer 18

Created by ice particles in clouds rubbing together and causing friction. Too of cloud is positive and bottom is negative. This builds up a static charge. If it’s big enough, the electrons can jump through the air to the earth

Question 19

Limiting dangers (lightning)

Answer 19

Attaching an earthing (metal) rod to the highest point of a building which provides a direct route for the electrons to go to the earth as it is a conductor

Question 20

Limiting dangers (sparks when refuelling)

Answer 20

Grounding rod is used. The person has to stand and hold it because they would be connected to the earth. Any charge is conducted to earth and charge can’t build up so there will be no sparks

Question 21

Electric field

Answer 21

The region where an electric charge experiences a force

Question 22

Key features in field lines

Answer 22

The direction (always positive to negative) and line spacing (smaller gal means more charge)

Question 23

Shape and direction of the electric field around a point charge

Answer 23

Positive charge in the middle. Electron field goes the other way (away from the middle)

Question 24

Shape and direction of the electric field between parallel plates

Answer 24

Field lines between the plates are uniform

Question 28

Electrostatic phenomenon (clothes)

Answer 28

In tumble drier or over the head. Electrons move from hair to jumper. Leaves static charges of attraction and little sparks as the charges rearrange themselves

Question 29

Electrostatic phenomenon (cars)

Answer 29

Static charge build between clothes and synthetic seat. Friction transfers electrons. When touch metal door handle charge flows and you feel a shock. Some cars have conducting strips to give a safe discharge to earth.

Question 30

Dangers of static electricity

Answer 30

Explosions from sparks igniting (in flammable gases)

Death from shock (charge flowing through the body and stopping the heart)

Question 31

Earthing in fuelling

Answer 31

Plastic is an insulator. Friction caused by the electrons rubbing against the pipe from the fuel