Transcript True or False?

True or False?
• A negatively charged object has an
excess of electrons.
• The positive charges move in a metal
to balance the movement of free
electrons.
• The amount of charge depends on
the mass of an object.
True or False?
• Uncharged materials cannot be attracted
by charged materials.
• The atoms in the metal plate of an
electroscope rearrenge to form eletric
dipoles when a charge approaches.
• The charges collected by the top comb of
a Van Der Graaf generator can distribute
around the metal dome because this is
connected with the comb by metal
connections.
Applied Electrostatics
Inkjet printer
Positive plate
Fine nozzle
Negative plate
• The ink droplets are charged as they thrust against the nozzle
• The droplets are deflected as they pass between two
electrically charged plates
A4 paper
• The amount of charge, i.e. the size and direction of the
voltage, on the plates keeps changing to drive each droplet to
the right place on your paper
• What charge will the droplets deflected upwardly have? Why?
They will be negatively charged, because -ve charges are attracted by the
positive plate at the top and repelled by the negative plate at the bottom.
Photocopier
Negative plate
Heated rollers
Toner (black
powder)
• The metal plate is electrically charged and the image to photocopy is
projected onto it
• The lighter parts of your image cause the light to shine on the plate, so
that the charge leaks away
• The charged bits attract black powder which deposits on the paper
• The paper is heated by the heated rolls, so that the powder sticks on it
Spray painting
Negative charge
Positive nozzle
• The spray nozzle is connected to a positive terminal, so the paint
droplets become positively charged
• This makes them repel each other, so the paint spreads out
• The object you are painting is connected to the earth (or to a negative
terminal)
• This attracts the paint, giving an even coverage