Static Electricity Flashcards
SI unit of electric charge
Coulomb (C)
What is the amount of charge carried by an electron
1.6 x 10^-19 C
Electrical insulators and Electrical conductors: Motion of charged particles
Electrical insulators: Charged particles are not free to move about
Electrical conductors: Charged particles are free to move about
Electrical insulators and Electrical conductors: Ability to conduct electricity
Electrical insulators: Low
Electrical conductors: High
Electrical insulators and Electrical conductors: Method of charging
Electrical insulators: Friction (Rubbing)
Electrical conductors: Induction
Electrical insulators and Electrical conductors: Examples
Electrical insulators: Glass, Perspex, Silk, Wool
Electrical conductors: Metals, Steel, Fluids with mobile charged particles
Electrostatic charging by friction
When insulators are rubbed together, electrons move from one insulator to the other. The electrons moved remain at the surface where the rubbing was. Insulator that gained electrons become negatively charged while insulator that lost electrons become positively charged
Charging conductors by induction
Induction is the charging of conductors without contact. Conductors cannot be charged by friction as mobile electrons can be easily transferred to and away from conductors
Neutralising charged insulators
A charged object is neutralised by discharging the excess charges on it.
Insulators can be discharged through heating or by providing humid conditions
Conductors can be discharged by earthing
What is electric force
An electric force is the attractive or repulsive force that electric charges exert on one another
What is electric field
An electric field is a region in which an electric charge experiences an electric force
Direction of electric field
The direction of an electric field is the direction of the force that would act on a small positive charge
Strength of electric field
The strength of an electric field is indicated by how close the field lines are to one another
Strength of electric field
The strength of an electric field is indicated by how close the field lines are to one another
Close together = Stronger
Further apart = Weaker
Electric field lines of parallel plates
The electric field lines start from the positively charged plate and end at the negatively charged plate. The field is uniform near the middle of the plates
Hazards of electrostatics: Lightning
-Thunderclouds are charged by friction between water molecules in the thunderclouds and air molecules in the atmosphere
-Negative charges accumulate at the bottom of the clouds
-These repel the electrons near the surface of the Earth, causing the surface of the Earth to be positively charged
-When the accumulation of charge is large, the air particles nearby are ionised
-The ionised air particles provide a conducting path for the electrons in the clouds to reach the Earth
-When the electrons travel down the conducting path to the Earth, lightning forms
Why is lightning considered a hazard
Damage to buildings and cars, and harm people
What safety measures are taken to prevent potential damage from lightning
-Lightning rod on buildings
-Lightning alert
-Closure of outdoor areas during thunderstorms
Hazards of electrostatics: Electrostatic discharge
-Excessive charges may build up on objects due to friction
-Electronic equipment, such as computer boards and hard drives, can be easily damaged by electrostatic discharge
-Such equipment are usually packed in antistatic packaging
Applications of electrostatics
-Photocopiers
-Spray painting
-Crop sprayers
-Electrostatic precipitators
