Static Electricity Flashcards
(14 cards)
What is the formula for calculating one coulomb?
1C = 1A x 1s, where s represents second
What is an electric field and what happens to its charges when it is not zero?
An electric field is a region where an electric charge experiences a force.
When the electric field is not zero, the electric charge experiences a net force.
What is the direction of field lines for an isolated charge?
For an isolated charge, the field lines extend to infinity.
If the charge is positive, the lines emanate from the positive charge and terminate on the negative charge.
How does the density of the field lines demonstrate the strength of the field?
A weak field has lines which are further apart from each other.
Densely packed lines represent a strong field.
What can shield electric fields and what is its significance?
Metals are able to completely shield an electric field.
In the lift, which is constructed entirely out of metal, it is impossible for the phone to reach a signal.
How are excess charges distributed across various shapes?
- For a spherical surface, all excess charges would be distributed equally across the surface.
- For other shapes, there would be more charges at the edges or vertices.
Category: Electric Charging
What is charging by friction/rubbing?
Charging by friction refers to the method of charging insulators by rubbing two insulators together, thereby causing the process of electron transfer from one insulator to another, thus causing that insulator to be charged.
Category: Electric Charging
What is charging by conduction?
Charging by conduction is the method in which a charged conductor is in direct contact with a neutral conductor. When this occurs, charges from the charged object are then transferred to the neutral conductor.
E.G charging of a metal sphere: A negatively-charged rod is placed into contact with the metal sphere, thus allowing electrons to flow to metal sphere, resulting in it being negatively-charged.
Category: Electric Charging
What is charging by induction?
Charging by induction refers to the process of redistributing electric charges when brought near a charged object, where opposite charges are brought to the side of the object that is closer to the charged object.
Category: Charge Polarisation
What is charge polarisation?
In a neutral atom, the centre of the electron cloud coincides with the positive atomic nucleus.
When a positively charged rod is brought near the atom, the electron cloud is electrically attracted to the rod, the and rod electrically repels the positive nucleus, resulting in the atom being polarised.
Category: Applications of Electrostatics
How are electrostatics important to spray painting?
Applying negatively charged paint to a positively charged surface can ensure that the spray painting is done very evenly. Any unpainted surface would produce an electric field that attracts the nearby paint to cover it. Any uneven paint surface would create a repulsive field that repels the similarly charged paint until it is smoothened out.
Category: Applications of Electrostatics charging
How are electrostatics applications important in the field of Electrostatics precipitators?
The smoke particles in the gas are streamed through a negatively charged grid, where each particle becomes negatively charged through charging via conduction. The negatively-charged particles would follow the electric field lines to the positively-charged metal plates, resulting in the smoke being separated from the gas. Knocking the plate would ensure that these particles fall and are collected in containers below.
Category: Electrical Hazards
How does a lightning hazard occur?
- Charge separation causes positive charges to accumulate at the top of the clouds, and negative charges to gather at the bottom.
- The earth’s surface directly below the cloud (eg tops of buildings) are induced a positive charge through electromagnetic induction, thus creating a strong electric field between the cloud and the ground.
- A sudden electric discharge (lightning) occurs to neutralize the charge difference.
Category: Electric Hazards
How do fire hazards occur in oil refineries?
A person may carry excess charges due to various reasons. When they come into contact with refueling equipment, these charges may suddenly discharge in the form of a spark. Even the smallest spark could ignite the highly flammable fuel vapours.
