Transcript 2. Static, from Daft to Dangerous

1. What charge does a polythene rod have after it has
2.
3.
4.
5.
6.
7.
8.
9.
been rubbed with a duster?
Name the particles that have moved to make this
happen.
Did these particles move from the polythene rod or
from the duster?
What charge does an acetate rod acquire when
rubbed with a silk cloth?
Name the particles that have moved to make this
happen.
Did these particles move from the acetate rod or from
the silk cloth?
What happens if two negatively charged objects are
brought near each other?
What happens if two positively charged objects are
brought near each other?
What happens if a positively charged object is
brought near a negatively charged object?
1. Negative
2. Electrons
3. Duster
4. Positive
5. Electrons
6. Acetate rod
7. They repel
8. They repel
9. They attract
Lesson.2: Static, from Daft to Dangerous
Objectives
Be confident in explaining some of the
phenomena involving static electricity in
some scientific detail.
List and explain some of the methods
for preventing the build up of static
electricity.
Earthing Safely
A charged conductor can be discharged by
connecting it to earth with a conductor.
Earthing, but not so safely
The greater the charge on an object, the greater the
voltage between the object and earth (0 Volts).
If the voltage becomes high enough, a spark may
jump across the gap between the object and any
earthed conductor which is near to it.
Lightning can be reproduced in the lab!
Van de Graaff time!!!
Van de Graaff time!!!
Do not touch the person on the platform
Always keep one hand on the Dome
Never step off the platform
Do not take part if you have any heart
issues
Discussion Card Activity.
The floor tiles in an operating theatre
are made of a conducting material.
Petrol road-tankers
usually have a length of metal chain
hanging down to touch the ground.
A mirror polished with a dry cloth on a
dry day soon becomes dusty.
The tanks of large ships are often filled
with nitrogen before cleaning with a
high-speed water jet.
It can be dangerous to use an umbrella
during a thunderstorm.
‘Cling film’ often sticks to itself
when pulled off the roll.
Aircraft tyres are made of a type of
rubber
that conducts electricity.
You should never shelter under a tree
during a thunderstorm.
When instant coffee is poured into jars
in a factory, it spreads out,
so some of the coffee misses the
jars.
Droplets of pesticide become charged
when applied using a spray gun.
Homework
Explain one of the static daft or dangerous
situations to somebody at home.
•
Describe and recognise that when some materials are rubbed they
attract other objects:
• small pieces of paper or cork to a rubbed comb or strip of plastic;
• certain types of dusting brushes become charged and attract dust as
they pass over it.
•
Recognise and describe how you can get an electrostatic shock from
charged objects:
• synthetic clothing.
•
Explain how static electricity can be a nuisance:
• dirt and dust attracted to insulators (plastic containers, TV monitors
etc);
• causing clothing to “cling”.
•
Recognise and describe how you can get an electrostatic shock if you
become charged and then become earthed:
• touching water pipes after walking a floor covered with an insulating
material e.g. vinyl.
• Explain how static electricity can be dangerous when:
• in atmospheres where explosions could occur eg inflammable gases
or vapours or with high concentrations of oxygen;
• in situations where large quantities of charge could flow through the
body to earth.
• Explain how the chance of receiving an electric shock can be reduced
by:
▪ correct earthing;
▪ use of insulating mats;
▪ using shoes with insulating soles
• Explain why it is necessary to earth lorries containing inflammable
gases and liquids and powders before unloading.
• Explain how anti-static sprays, liquids and cloths help reduce the
problems of static electricity.