6 Flashcards
Describe how friction causes static electricity?
Insulated materials that rub together shift negatively charged electrons from one to the other. Now one has more electrons than the other, these causes static electricity.
State some dangers of static electricity.
Refueling cars, Static on airplanes and lightning.
Explain how photocopiers use static electricity?(5)
When paper is put into the photocopier, a light beam is shone down at the paper.
Where the image is white the light reflects through the paper onto a drum.
On the drum is a lot of negatively charged toner. Where the light beam hits the drum the toner is neutralised by the positively charged photon beam.
A sheet of paper that has been positively charged passes over the drum and all the negatively charged toner is attracted to the paper and activates on impact creating an image.
Explain how industrial chimneys use static electricity?(4)
Dust and smoke created by the chimney passes through two filters called electrodes.
The first electrode is very negative voltage which will cause all the smoke passing through to become negatively charged.
The second electrode is very positively charged and is met by the smoke after the first filter.
All the negatively charged smoke particles are attracted to the filter and stick to it reducing fumes that go into the air.
Explain how electrostatic sprayers use static electricity?(4)
The spray gun is charged which charges up all the drops of paint released by it.
Each paint drop repels all the others so there is a very fine even spray.
The object being painted is given an opposite charge to the gun so it attracts the paint drops.
Therefore all the paint spreads evenly across the bike and also doesn’t drip because it is attracted to the object.
Describe electric fields briefly?
Flow from positive to negative, always a right angle to the surface, created by electric charges.
Describe what a uniform field is?
When two opposite poles are put parallel or near each other this creates a uniform field. Lines in a uniform field are parallel to each other and each the same distance apart.
Explain how compasses work?
Inside a compass is a tiny bar magnet called a needle. The needle always lines up with the magnetic field it’s in. If a compass is not near a magnet it will point to the Earth’s Geographic North (Magnetic South) Pole.
What are the three main magnetic elements?
Iron, Nickel and Cobalt. However, alloys and compounds of these metals are also magnetic such as steel.
What are the two types of magnets?
Magnetically ‘soft’ or ‘temporary’ magnets and magnetically ‘hard’ or ‘permanent’ magnets. Magnetically soft materials are things like pure iron while magnetically hard are things like steel.
What are some uses of magnets and electromagnets?(4)
Fridge doors use a permanent magnetic strip to keep it closed. Cranes use electromagnets to pick up and move magnetic materials. Doorbells use electromagnets to rapidly turn on and off to release and strike an alarm. Maglev trains use magnets to make trains float slightly above the track.
What is Fleming’s left-hand rule?
Flemings left hand rule is used to find the direction of the force on a current carrying conductor. Point the first finger in direction of magnetic field and your second finger in direction of Current and the thumb will point in direction of motion.
State the force equation when the current is at 90 degrees to the magnetic field it’s in.
Force(F) = Magnetic flux density(B) x Current(I) x Length(L)
(N) (T, Tesla or N/Am) (A) (m)
Describe what a solenoid is?(3)
A solenoid is a long coil of wire with lots of loops.
Inside the solenoid lots of field lines point in the same direction but outside the overlapping field lines cancel each other out.
This means that the field lines end up the same as around a bar magnet. A solenoid is an electromagnet.
State three ways to increase the strength of a solenoid.
- Wrap more turns in the coil
- Put a block of iron(or other soft magnet) in the centre of the coil
- Increase the current
