Science- Static Electricity

How does a lightning rod reduce the likelihood of a lightning strike?

-either the charges streaming between the cloud and lightning rod tend to neutralize each other which can be enough to prevent lightning from striking. -or the rod can conduct the charge safely to the ground since the lightning will likely hit the rod instead of the building

Applications of induction

-neutral dust particles are attracted to a tv or computer screen due to a charge imbalance -electrostatic lifting apparatus: footprints at crime scenes - electrostatic aircleaners clean air by charging dust particles

Electrostatic precipitators

Reduces pollution because it reduces air pollution from dust particles and liquid droplets by making the particles and droplets positively charged when they come in contact with the wire with a strong positive charge. The positively charge particles and droplets then induce a negative charge on the collection plates. When they then collide with this plate they are neutralized and collect in containers called hoppers.

Charging an object

Results in a shift of charges. Only electrons can be moved and result in a charge. There are 3 methods of charging an object: 1. Friction 2. Contact 3. Induction

The Laws of Electric Charges

States that like charges repel one another and unlike charged attract one another. Neutral objects are attracted to charged objects.

How are airplanes protected from static charges building up on the aircraft?

Static wicks on the wings protect the plane.

Who was the first person to recognize the static effect?

Thales. He was rubbing amber. The greek word for amber is electron.

What creates thunder?

The compression and expansion of hot and cold air.

Charges at work

-a ground strap is used to remove static charges on vehicles -needle like rods on wing of an airplane dispense static charges into the air -using a dryer sheet adds a thin layer of waxy chemical to the surface of clothes so there is less friction

Discharge

Letting the charge "jump off" or getting rid of the charge. They can be visible as Sparks and the greater the charge imbalance, the more noticeable the discharge will be. They can damage circuits in electronic equipment.

Third step in the formation of lightning

Lightning -once the step leader and streamer connect, the connection between cloud and earth is formed and a rapid discharge of electrons (lightning) occurs into the ground

Semi-conductors

Materials like carbon and silicon that electrons can not move as easily through.

When charging objects by friction:

-Both objects are neutral before they are rubbed together -One object is more likely to accept the electrons and will become negatively charged -Objects become more easily charged in the winter because there is less water in the air that can accept extra electrons.

When charging by contact:

-Electrons transfer from the charged object to the neutral object it touches. The neutral object gains the same type of charge. -Electrons always move from the object with a greater negative charge to the object with the least negative charge. -Always results in the charging object and the receiving object having the same type of charge

Conductors

-Materials that permit the movement of electrons (copper, aluminum). Electrons can move freely from atom to atom. Electrons can be sent (conducted through these) -They are used in wiring -Water is a conductor

Insulators

-Materials that prevent the flow (movement) of electrons, (plastic, ebonite, wood, glass). Electrons can't be sent (conducted) through these. -Plastics are used around wire because they are these and can prevent electrons from escaping and protects us.

Charging by Contact

Occurs when two objects with different amounts of electrical charge come in contact.

How are gravitational and electrical forces similar?

-They both deal with the force between two objects -As you increase the distance between the two objects the forces are between the charges decrease -different because of what they deal with -different because electricity can be both attractive and repulsive but Gravity is only attractive

How much electricity can be found in a single bolt?

100,000,000 bolts

What temp does lightning heat the air to?

30,000º

How many lightning bolts hit the ground every second on earth?

50-100

What type of path does lightning form?

A jagged irregular path since it follows the path of least resistance in the air.

Electrostatic Series

A list of material based on their electron affinity (ability to hold electrons). It is a list used to determine the strength a object has when holding on to its electrons and allows us to predict the movement of electrons. The higher the material in the list the greater its tendency to lose electrons.

What is another name for a static electricity generator?

An Electroscope.

Static cling

An electron build up- negatively charged.

Van de Graaf generator

Can accelerate particles to very high speeds, then can focus the beams of particles at each other so they crash into each other, breaking the particles into fragments and sometimes forming new subatomic particles. Can accumulate and transfer very large charges. A sphere rests on an insulated column that has a rubber belt inside which runs over two rollers. A motor drives the lower belt and as the belt moves over it, charging by friction takes place. The charges stick to the belt and the are carried up to the top of the roller to a metal collecting comb, which is attached to the sphere. The charged belt induces a redistribution of charges on the comb. The charges then accumulate on the metal sphere where they can be transferred to anything that touches it.

Charging by induction

Charging a neutral object without touching. This always results in the two objects having opposite charges.

Grounding

Connecting an object to the earth so that it can share its charge with the whole earth.

What causes static on the radio or television?

Dust and water vapour in the air that electrons pick up cause this.

Electrostatic dusters

Duster becomes charged which attracts dust particle (neutral)

First step in the formation of lightning

Formation of a step leader: -comes from the bottom of a cloud -a negative stream directed towards the ground

Second step in formation of lightning

Formation of streamers -the ground area under the step leader forms a positive charge since the electrons repel from step leader - air above ground become positive and moves towards the step leader -streamers form from highest object under the step leader (less distance to the step leader)

Humidity/water and electricity

Humidity refers to the amount of water in the air (an insulator). Water droplets help discourage static electricity by picking up extra charges and transferring them elsewhere. Because there is less water in the air in the winter (as the temp decreases the air's ability to retain water decreases). Therefore static charges build up more in the winter than in the summer when its humid.

Permanent charge (permanent induction)

If the neutral object is grounded, some of the electrons leave or enter the object and it can become permanently charged.

Where is the safest place to be in a lightning storm?

In your car.

Why is lightning dangerous?

It carries a very large electrical current that will damage any unprotected tree, building or person it hits and can also create forest fires.

What is Static Electricity?

It is electricity at rest (stationary electrons). It involves the buildup of electrons within/on the surface of an object. The charges are "static" because they remain in one location on the surface of an object until they are given a path to escape.

Why is it important for a pith ball to be small?

It is important for it to have a small mass because since it is small the electric force produced by the charged object will be enough to move it.

Photocopiers

The document you want to copy is place on the glass, and a bright light scans across it. The shadow forms on the photoconductor, darker in spots where there is ink. The photoconductor is coated in selenium which produces a positive charge in the dark. An ink drum carrying toner then coats the belt with toner, which is negative and therefore attracted to the positively charged dark spots. A sheet of paper is then fed toward the first belt and is given a strong positive charge (stronger than the first drum) so the negatively charged toner will stick to it. The inked paper then passes through heat rollers which fuse the particles onto the paper permanently. The final copy then emerges, still warm.

Why does a person's hair stand on end when they touch a static generator?

The electrical charge runs through the person's arm up to the highest point of their body- their hair. Since the electrons are not attracted to each other the person's hair stands on end and repels.

What happens when a charged object is grounded?

The electrons travel from the object to the ground through a ground wire until the object is neutral, It is the ground wire that allows the electrons to get to or from the ground quickly and efficiently.

Temporary charge (induced charge separation)

The object remains neutral, however, electrons rearrange themselves within the object causing it to become charged. Once the charged objects is removed, the electrons can redistribute themselves within the object. Protons do not move.

Electron

The only subatomic particle that can be transferred from one object to another.

electrostatic spray

The paint or powder is given a charge as it leaves the nozzle of the sprayer. The object being sprayed is then given an opposite charge of the particles or is grounded so that the particles in the spray are attracted to the objects being coated which minimizes overspray.

Charging by Friction

The transfer of electrons by rubbing or touching.

Lightning

The transfer of electrons from a cloud to the earth or to another cloud. Moves in the path of least resistance. Lightning rods are often placed on the tops of buildings to reduce the damage from this.

Why are gas stations and oil refineries dangerous?

They are dangerous to work at because the fumes they work with are explosive. Since they are explosive, any static charge can ignite the fumes and cause them to explode. Precautions are taken though. The refinery or gas station is grounded so that any excess charge is neutralized before it can cause something to explode.

How can objects become charged?

They can become charged when electrons move from one object to another. Most of the objects we use daily are electrically neutral. However when two objects made of different materials are rubbed together, the friction produces a charge imbalance.

How long can a lightning bolt be?

Up to 140 km long.

How can positive ions move through the air?

When a large negative charge is within 100m of the ground and the large amount of positive ions are attracted to the negative charge and jump to meet them.

Releasing charges

When an object is charged the charges are trapped on the object until they are given a path to escape. When those charges are quickly transferred it is called a discharge.