Electrostatics Flashcards
Def the law of attraction and repulsion
The law of Attraction and Repulsion between charged particles states that
like charges repel and
unlike charges attract
Def the law of Conservation of charges
the law of Conservation of charges states that
Charge cannot be created or destroyed, but can be transferred from one object to another
How is a body charged by rubbing
The production of charges by rubbing is caused by a transfer of electrons from one material to the other
What happens when Polythene is rubbed with flannel
The polythene becomes Negative
Flannel becomes positive
Friction removes the electrons from the flannel
Electrons are added to the Polythene
Remember. The t in polythene has a - through.
What happens when Perspex is rubbed with Silk
Perspex becomes +
Silk becomes -
The friction cause the loss of electrons from the perspex, leaving the perspex positively charged while the silk gains the electrons, making the silk negative
Remember. The X in PerspeX is a + sign turned scew
Def a good conductor
a good conductor is a material through which electrons flow freely
Def A good insulator
A good insulator is a material through which electrons cannot flow freely
Which materials will be charged best by rubbing them
Good insulators
Because the charge produced cannot move from where the rubbing occurs
Def. Electrostatic induction
Electrostatic induction is
the charging of neutral objects
by the close proximity of a charged object
which does not make contact with the neutral object
Describe how two neutral spheres can be given equal but oposite charges by induction
Let two spheres touch
Bring positively charged rod in close contact to one of the spheres
Move the spheres apart whilst rod is still in same place
Remove rod
Now 2 spheres are equalli, but opposite charged
Name some facts about electrostatic charge
The unit of charge is the Coulomb
1 coulomb of charge = quantity of charge on 6,25 x 10 ^18 electrons
A positively charged body has a deficiency of electrons
A negatively charged body has an excess of electrons
How does attraction between a charged and uncharged object take place?
Due to induction
Give an example of how attraction between a charged and uncharged object take place
A negatively charged polythene rod held close to a neutral piece of aluminium foil attracts it
The charged rod repels the mobile electrons of the aluminium foil to the far side of the foil leaving a positive charge on the surface closest the rod
Now the attraction forces between the negatively charged rod and positive side of the foil is greater than the repulsion forces (of the negative charged rod and negative side of the foil) due to the difference in distance
Describe how paper, which is an insulator without free electrons, can be attracted by a charged rod
Even though it does not have free electrons, a charge is induced by a distortion of the electron clouds of the atoms
What is the instrument called that you can use to show the presence of an electric charge
Electroscope
Remember. Electro - that is what we want to look at
Scope - what we use to look with
Name 4 things that a electroscope can be used for
- To show the presence of an electric charge
- To test whether an electric charge is positive or negative
- As a Voltmeter requiring no current from the circuit
- To test the quality of electrical insulating materials
Draw a electroscope with annotations
Metal cap
Insulating material
Metal rod
Metal case
Gold lead
Glass front
Earth
How do you charge (by touch) an electroscope that is neutral
Touched by an object that is charged
Remember. Perspex rubbed with silk become positive
Polytene rubbed with flannel become -
Describe how an electroscope can be charged by induction
- Bring a - charged rod in close contact to the cap of the electroscope. Gold leaf is deflected
- Earth the electroscope by touching the cap. Gold leaf collaps, because excess electrons flow away. Cap stays positively charged due to - charged rod
- Take negative charged rod away - electrons in goldfoil redistributes, leaving an overall + charge. Gold leaf deflects again
How do we test for a charge using the electroscope
Charge a electroscope with a known charge. Bring the unknown charge in close proximity of the electroscope
Similar charges will cause the gold leaf to deflect even more.
Dissimilar charges will cause gold leaf to collapse.
Def an electric field
an electric field is a region in space in which an electrical charge will experience a force
What is a field line
It is a representation of an electrical field
How will you determine the direction of a field line
It is the direction of force on a small positive test charge placed at that point
Name 5 properties of field lines
- The direction is from + to -
- Field lines never cross
- Field lines occur in 3 dimensions, not only in the plane of the paper
- Field lines are closer in regions in which the field is strong and further apart where the field is weak
- An electric field is continuous (a limited number of field lines are drawn on paper to represent the field)
Name 4 applications where we use electrostatics
- Van de graaf generator
- Photocopier
- Flue ash prescipitation
- Inkjet printers
If 2 charged objects attract each other, the charges on the objects are…….
Unlike
What happens to the goldleaf of a positively charged electroscope when a negatively charged rod comes in close proximity of the electroscope
The goldleafs will collaps / fall / return to their original position
A positively charged rod is brought close to a charged electroscope. The goldleave is repelled further. It can be concluded that the electroscope was …..
Positively charged
An electroscope is charged positively by direct touch of a rod
What charge did the rod have
+
A electroscope is charged positively by induction
What charge did you have on the rod
-
Draw the symbol for earth
A
Make a neat sketch to illustrate the electric field around two positively charged spheres
A
Give an example of a good conductor
Iron
Copper
Give an example of a good insulator
Wood
Plastic
Rubber
Paper
A separation of charge on an object through the close proximity of another charged object without contact is called ……….
Electrostatic Induction
