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10 Cards in this Set
- Front
- Back
- 3rd side (hint)
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What is static electricity? |
-When certain insulating materials are rubbed together, negatively charged electrons will be scraped off one and dumped on the other. -As the materials are insulators, these electrons are not free to move, and the build up of charge is static electricity. The materials become electrically charges with a positive static charge on the one that has lost electrons and an equal negative static charge on the other. -Which way the electrons are transferred depend on the 2 materials involved (you don’t need to figure out which one) and electrons are always moved. |
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Charges repealing and attracting |
Opposite charges attract, how strong depends on the strength of their charge. Like charges repel, again depending on their strength. The forces get weaker the further part the two are. |
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Electrically charged objects can attract uncharged objects |
-rubbing a ballon on your hair transfers electrons to the ballon, leaving it with a negative charge. If you hold the ballon against a wall it will stick, even though the wall does not have a charge. -This is because the charges on the wall can move a little- the negative charges on the ballon repel the negative charges in the surface of the wall. -This leaves a positive charge on the surface, which attracts the negatively charge balloon. Called attraction by induction. |
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How does too much static cause sparks. |
-As electric charge builds in an object, the potential difference between the object and the earth (which is 0v) Increases. -If the potential difference gets large enough, electrons can jump across the gap between the charged object and the earth- this is the spark. -They can also jump to any earthed conductor that is nearby- which is why you can get static shocks from clothes or getting out of the car. -This usually happens when the gap is fairly small (but not always- lightning). |
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Uses of static electricity. |
-one example: electrostatic sprayers: -Electrostatic sprayers are used in various industries to give a fine, even coat of whatever’s being sprayed eg bikes and cars. -The spray fun is charged, which charges up the small drops of paint. Each paint drip repels all the others as they have the same charge, so you get a very fine even spray. -The object to be painted is given and opposite charge to the gin so it attracts the paint. -This method gives and even coat and hardly any paint is wasted, and parts pieuvres away from the spray gun also get coated. |
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Dangers of static electricity. |
-Refuelling cars- as fuel flows out of a fuller pipe, static can build up. This can easily lead to a spark which might cause and explosion in dusty of fumes places. -Static In airplanes- as planes fly through the air, friction between the air and the plane caused the plane to become charged. This build up of static charge can interfere with communication equipment. -Lightning- raindrops and ice bump together inside storm clouds, leaving the top of the cloud positively charged and the bottom of the cloud negative. This creates a huge voltage and a big spark, which can damage homes or start fires when it strikes the ground. -You can reduce some of these problems by earthing charged objects. |
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What does earthing objects do? |
-Dangerous sparks can be prevented by connecting a charged object to the ground using a conductor- this is called earthing. -Earthing provides and easy route for the static charge to travel into the ground. This means no charge can build up to give you a shock or make a spark. -The electrons flow down the conductor to the ground if the charge is negative and flow up the conductor from the ground if the charge is positive. -Fuel tankers must be earthed to prevent any sparks that might cause the fuel to explode. |
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What creates an electric field? |
-Creates around any charged object. It’s the region around a charged object where, if a second charged object was placed inside it, a force would be exerted in both of the charges. -The Closer to the object you get, the stronger the field is. -You can show an electric field around an I j’écris using field lines. |
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How do electric fields cause electrostatic forces? |
-When a charged object is placed in an electric field, it fells a force. This force is caused by the electric fields around 2 charges objects interacting. -If the field lines between the charged object point in the same direction, the field lines join up and the objects are attracted to each other. -When the field lines between the charged objects point in opposite directions, the field lines ouch against each other and the objects repel each other. -Between two oppositely- charged parallel plates, you get a uniform field that looks like this (see hint). -The strength and direction of the field is the same anywhere between the 2 plates (it’s only different at the very ends). |
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Explain sparking? |
-Statically charge objects generate its own electric field. -Interactions between this field and other objects are the cause of events like sparking. -Soarks are caused when there is a high enough Pd between a charged object and the earth (or earthed object). A high Pd causes a strong electric field between the charged object and the earthed object. -The strong electric field causes electrons in the air particles to be removed (known as ionisation). -Air is normally an insulator, but when it is ionised it is much more conductive, so a current can flow through it. This is the spark. |
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