07. Static Electricity and Capacitance

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1
*If an object is negatively (–) or positively (+) charged...
– : It has gained electrons
+ : It has lost electrons
2
Insulator
A substance through which electric charge cannot flow
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Conductor
A substance through which electric charge can flow
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*Examples of conductors (4)
*Silver, Copper, Aluminium
Water
Human Body, The Ground
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*Examples of insulators (4)
*Glass
Plastic
Rubber
Air
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*1 Coulomb is the amount of charge on how many electrons?
*6.25 × 10¹⁸
1 ÷ (electronic charge, log tables)
7
*Where is static electricity on a conductor????
*on the outside
it gathers where the conductor is most pointed
8
Coulomb's Law
States that the force of attraction or repulsion between two point charges is directly proportional to the product of the charges and inversely proportional to the square of the distance between them.
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1 Coulomb
1 Coulomb of charge passes a particular point when 1 A of current flows for 1 second

*check*
10
*relative permittivity formula
*
ε= εr × ε0
medium = relative permittivity × vaccuum
11
Electric Field
any region of space where electric forces can be felt
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*What is an electric field is caused by
*An electric field is always caused by other static charges in the vicinity.
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*Line of Force (Electric Field Line)
*a line drawn in an electric field showing the direction of the force on a positive charge placed in the field.

**check asterisk**
14
Electric Field Strength
The electric field strength at a point is the force per unit charge at that point
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*Unit of Electric Field Strength
*N / C = V / m
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Potential Difference
The work done per unit charge moved between two points.
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1 volt
The potential difference between two points is 1 volt if 1 J of work is done in bringing 1 C from one point to the other
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Electric Current
a flow of electric charge
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Potential at a Point
The potential difference between a point and the Earth
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Capacitance
Charge per unit voltage
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The farad
A conductor has a capacitance of 1 farad if placing a charge if 1 C on it raises its potential by 1 V
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*Use of Capacitors
*Camera flash gun
Smooth out variations in direct current
23
*Difference between Coulomb's Law and Newton's Law of Universal Gravitation
*Charge vs Mass
Attraction & Repulsion vs Only Attraction
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