Physics- Electricity Flashcards
List three examples of static electricity:
-Bending Water with a comb
-Balloon held against wall
-Shocks from carpets, etc
What does Friction cause?
The transferance of electrons from one material to another.
Describe Electron transfer
Friction causes electrons to transfer between the two objects.
Therefore, one object GAINS extra electrons, forming a Negative charge, while the other object LOSES electrons, forming a Positive charge (note that both objects originally had a neutral charge).
If a negatively - charged rod is placed on the neutral paper…
The negatively charged rod repels the electrons on the neutral paper, leaving more protons near the surface, so the paper is attached to the rod as opposite charges attract.
Which subatomic particle can move.
Electrons can move as they are free and flexible and Protons and fixed.
How are Sparks formed?
Electrons try to dissipate the electrostatic charge by finding the quickest way to Earth.
When a person builds up a static charge, it stays with them, as long as they are insulated from the ground.
The charge will slowly leak away but can be redistributed onto something else; this is even more effective if a conducting material is touched.
When two charged objects come close together and the field is strong enough, there is a potential difference (difference in amount of energy) between them- causing this large amount of energy to transfer , as it travels quickly through an air gap, a Spark occurs.
Why does the Van De Graaf machine make your hair stand on end?
The machine builds up a static charge when a rubber belt, driven by a motor, transfers this static charge to the dome. As more and more electrons accumulate on the dome, the voltage difference between the dome and the ground increases, creating a strong electric field. The charge stays in the dome until it has a means to travel to the Earth (through the person). Your hair stands on end as if there is a charge travelling all through the body; as each strand of hair has the same charge, they will repel each other, making them stand on end.
How is it safe to touch a Van De Graaf machine?
Although the Voltage is high, the current is low.
How are sparks caused from Van De Graaf machines?
A Van de Graaff generator produces sparks by building up a high static electric charge on a metal dome and then discharging it through the air.
But why?
When a grounded object (like a metal rod or your hand) is brought close to the dome, the electric field between the dome and the object becomes extremely strong. At a certain point, the electric field becomes strong enough to ionize the air molecules in the gap between the dome and the object.
The ionized air becomes conductive, and the charge from the dome jumps across the gap as a spark. This spark is a temporary discharge of the accumulated charge
Why does static charge only build up on Insulators and not Conductors?
Conductors can’t easily hold a static charge because their electrons can move freely within the material, preventing charge buildup. Any excess charge will rapidly redistribute and flow away from areas of high charge concentration.
When may we feel a shock?
We may feel a shock when touching an object that has static charge built up upon it.
What is an electric field?
An electric field is the area around a charged object in which a force can be exerted or experienced by another charged object.
What determines the closeness of the field lines?
The stronger the charge of the object, the stronger the field strength, therefore the greater the force experienced, and so the field lines will be closer together.
What is a Radial Field?
A Radial Field is an electrical field represented by towards or away from a point.
What is a Point Charge?
A negligibly small charged object.
Describe the Field lines in radial fields, including attraction and repulsion between radial fields.
Field lines always move away from a POSITIVELY charged object and towards NEGATIVELY charged objects.
When two fields come close to each other, the field lines distort.
Remember, it’s always FROM the POSITIVE field to the NEGATIVE one. With two alike fields, they go away from one another (repulsion).
What is a Uniform field?
A field where the magnetic field strength and direction are the same at all points of the object. -The field lines are equally spaced.
-This may occur between two parallel charged plates, such as in a Capacitor ( a component that stores charge).
Describe TWO dangers of electrostatics:
1) In the presence of fuel and Oxygen, an electrostatic spark may provide an ignition source to start a fire.
2) When refuelling aircraft, the friction between the fast-flowing fuel and the hose could create a static spark and ignite the fuel.
How can we prevent fires from electrostatics?
An Earth wire between the aircraft hose and the ground can safely take the charge away.
Name two USES of electrostatics:
1) Electrostatic Precipitators (for removing smoke from factory emissions)
2) Paint Sprayer for painting cars
