Topic 11

Question 1

Explain how an insulator can be charged by friction, through transfer of electrons

Answer 1

• insulating materials rubbed together, negatively charged electrons scraped of one and dumped on other.
• as materials are insulators, electrons aren’t free to move-this build or charge is static electricity. Materials become electrically charged, with positive static charge on one that lost electrons and an equal negative static charge on other.

Question 2

To like charges …

Answer 2

Repel

Question 3

To unlike charges …

Answer 3

Attract

Question 4

Explain shocks from everyday objects and lightening in terms of movement of electrons

Answer 4

As Electric charge builds on object, potential difference between the object and earth increases. If pd gets large enough, electrons can jump across gap - the spark. They can also jump to any earthed conductor nearby- shock

Question 5

Explain attraction by induction in terms of movement of electrons. Balloon

Answer 5

Rubbing balloon against hair/clothes transfers electrons to balloon, leaving it with negative charge. Hold balloon against wall it will stick because charges on surface of wall can move- the negative charges on balloon repel negative charges on surface of wall, leaving positive charge on surface, which attracts negatively charged balloon.

Question 6

Explain attraction by induction in terms of movement of electrons. Comb

Answer 6

Run comb through hair, electrons transferred to comb making it negatively charged. It can then be used pick up piece of uncharged paper, holding near paper causes induction in paper, means they jump up and stick to comb

Question 7

Explain how earthing removes excess charge by movement of electrons

Answer 7

Earthing provides easy route for static charges to travel into ground. Means no build up of charge to give shock or spark. Electrons flow down conductor to ground if charge is negative and up conductor from ground if charge is positive

Question 8

Use of electrostatic charged in insecticide sprayers

Answer 8

-spray gun charged, which charges up small drops of insecticide. Each insecticide drop repels all others,since got same charge, so you get fine, even spray. Plants charge by induction as insecticide droplets come near them

Question 9

Describe some of the danger of sparking in everyday situations: refuelling cars

Answer 9

as fuel flows out of filler pipe static can build up, can easily lead to spark , might cause explosion in dusty/fumey places

Question 10

Describe some of the danger of sparking in everyday situations: lightening

Answer 10

Raindrops and Ice bump together inside storm clouds, leaving top of cloud + and bottom - . Creates huge voltage and big spark can damage homes/ start fires

Question 11

Describe some of the danger of sparking in everyday situations: static on airplanes

Answer 11

friction between air and plane causes plane become charged. Build up of static charge can interfere with communication equipment

Question 12

Define an electric field

Answer 12

The region where an electric charge experiences a force

Question 13

Describe the shape and direction of the electric field around a point charge and between parallel plates and relate the strength of the field lines to the concentration of lines

Answer 13

• electric field lines go FROM positive TO negative

- closer together lines are, stronger the field is

Question 14

Explain how the concept of an electric field helps to explain the phenomena of static electricity

Answer 14

When objects becomes statically charged, it generates its own electric field. Interactions between this field and other objects are the cause of events like sparking.