Electricity Flashcards
What is static electricity
Static electricity is the build up of charge caused by an imbalance of electrons on the surface of a material
Why does static electricity occur best at insulators
Electrons in insulators cannot move and thus cannot escape the the object, allowing for the build up of static electricity
What are conductors
Conductors are materials that allow electricity to flow through them. They have free moving, delocalized electrons that can move freely between them
What are insulators
Insulator’s are materials that cannot conduct electricity
List some examples of conductors
Metals
Graphite
Water
People
List some examples of insulators
Plastic
Glass
Rubber
Porcelain
What are some everyday examples of static electricity
Lightning
Rubbing a balloon on your hair causes it to stick onto them
What are two ways to create static electricity
Friction
Induction
How is static electricity created by friction
When a cloth is rubbed against an object, some electrons are rubbed off onto the object because of friction. This increase in electrons leads to the object acquiring a negative charge as it has more electrons than protons
Similar charges….
repel
Opposite charges…..
attract
Why is charge not built up when you are holding a conductor
Conductors are materials that allow electricity to flow through them. Therefore, when rubbing a conductor, the extra electrons can just escape from the object to your hands and then to the ground because of the presence of a conducting path
How does an electroscope become charged by induction
When a negatively charged object is brought close to the electroscope, the electrons in the electroscope are repelled by those of the object, causing them to move to the bottom. This results in both the metal rod and the leaf acquiring a negative charge. Since they both have the same charge, the leaf will be repelled by the rod causing it to rise
How does an earthed electroscope become charged by induction
When a negatively charged object is brought close to an earthed electroscope, the electrons in the electroscope are repelled by those in the object. Because of the existence of a conducting path, these electrons can escape to the ground, resulting in the electroscope acquiring a positive charge. Since both the rod and the leaf have the same positive charge, they repel causing the leaf to rise
How does a photocopier work
The copying plate is positively charged and an image of the page you want to copy is projected on the plate. The surface then is covered with negatively charged black power, which is attracted to the positively charged image area. Lastly, the powder is the fused to the paper by heat
How do inkjet printers work
Firstly, charged droplets of ink are forced out of a thin nozzle and passed between two oppositely charged metal plates. These droplets are attracted to the plate with an opposite charge and repelled by the plate with a similar charge, causing them to deflect as they pass between the plates. By controlling the size and the direction of the voltage applied on the plates, each droplet can be deflected to a particular place on the paper. Many dots like this produce printed characters
How does electrostatic painting work to paint a bicycle
The metal spray and the bicycle frame are given opposite charges, where one is positive and the other is negative. As droplets leave the spray gun and approach the bicycle frame, they repel each other and spread out due to the fact that they have the same charge. This results in the formation of a fine spray. Further, because of the opposite charge between the bicycle frame and the droplets, they attract each other and the droplets manage to stick to the bicycle
How do electrostatic precipitators
As smoke particles pass through a mesh of wires, they gain a negative charge. The smoke is then passed through another plate that is positively charged. This leads to the charged particles being attracted and sticking onto the large plates, resulting in cleaner smoke being released to the atmosphere, while dust and ash is left behind
Why does lightning occur
Due to the low temperature inside the clouds, ice forms, causing ice particles to bump into each other and resulting in separation of charges occurring . The positive charges go to the top of the cloud, while the negative charges are at the bottom of the cloud. These negative charges induce positive charges in the ground by repelling electrons. If the potential difference gets big enough, a spark will jump
