Section 2: Electric charge Flashcards
1
Q
Gold leaf electroscope
A
Detects electrical charges
-charging by induction-
1. Positive rod brought close, leaf goes up
2. Finger brought close, electrons run down the GLE to make it neutral, leaf down.
3. Remove finger then rod, positive has gone, but GLE gained more electrons, leaf rises.
GLE is negative
2
Q
Spray painting
A
- Gun is positively charged
- Every droplet is + so they repel each other (to create a even, fine mist)
- A wire makes the frame negatively charged
- Positive droplets attracted to negative frame
- less paint wasted
- front and back painted at the same time
- better quality finish, more even
3
Q
Electrostatic precipitator
A
- Used to pick out smoke particles in waste gases
- Collected because it could damaged buildings and breathing difficulties
- Attached to chimneys
1. Waste gases passes through a +/- charged metal grid
2. Picks up +/- charge
3. Attracted to oppositely charged metal collecting plates, which are knocked together to remove smoke particles
4
Q
Ink jet printer
A
- Each droplet of ink is given positive charge as it’s fired from the nozzle
- Droplets pass between pair of oppositely charged plates which attract/repel droplets
- The amount of deflection, hence the position of the position of the ink, is determined by the amount of charge on plates. This is controlled by the computer.
5
Q
Ballon experiment thingy
A
Before: ceiling is neutral During: -negatively charged ballon brought to ceiling -repels electrons in ceiling -ceiling around ballon positive -positive attracted negative Eventually: -charges leaks away from balloon, making it neutral -electrons in ceiling move back -no force on ballon so it falls
6
Q
Acetate
A
-Friction causes electrons to jump from acetate to duster
-becomes positively charged
-electrons attracted to the top of the GLE and leaf rises since both positive so repel
~A is positive!~
7
Q
Photocopier
A
- Copying plate is given a charge
- Image of page to be copied is projected onto the charged copying plate
- Where light hits the page the charge leaks away, leaving a pattern
- black ink powder is attracted to the charged parts of the plate
- Powder is transferred on paper
- Paper heated so powder melts and sticks to paper
- It’s now a photocopy of the original
8
Q
Discharging (a van de graaff generator)
A
- Electrons run down the metal wire from the dome to earth, leaving the dome neutral
- Electrons run up the metal wire from Earth to dome, leaving the dome neutral
- If an object has too many charges to cope electrons might jump through the air to discharge the object. This is called a spark👻
9
Q
Lightning
A
- Buildings are protected from lightning by lightning conductors which provide the path of least resistance from lightning to ground
- LC are sharp metal rods which are fixed to the top of a building
- The bottom of storm clouds are -ve so they induce + charge on the point of the rod as electrons are repelled
- Being the tallest + object around, lightning would hit the rod and travel safely to earth where it will dissipate harmlessly
10
Q
Dangers of refuelling a plane
A
- Body of the plane charges up due to friction cause by flying
- Plane lands on rubber tyres which is an insulator so plane stays charged up
- Kerosene truck comes and is also charged from friction of sloshing oil
- When a pip is put from the truck to the plane to refuel it causes more friction
- With all this charge around it could cause a spark which could cause an explosion from the fuel vapour
- To avoid this a metal chain is attached to the plane and the truck. In between it will run down to the earth and to make everything neutral
- You can also put some metal into the tyres so it acts as a conductor and the charge runs down into the earth
11
Q
Polythene
A
- Friction causes electrons to jump from duster to polythene
- It becomes negatively charged
- Electrons repealed to the bottom
- Leaf and bottom of rod(GLE) negatively charged so they repel, leaf rises
