Electrostatics and Magnetism Flashcards
what is the unit used to measure charge?
coulombs (c)
which charges attract and repel?
opposite charges attract and like charges repel
what are atoms composed of?
- protons
- neutrons
- electrons
what are the charges of protons, electrons and neutrons?
- protons: +1
- electrons: -1
- neutrons: 0
what does charging a body do?
involves the addition or removal of electrons- charging atoms creates ions
what do conductors do when touching electrons compared to insulators?
conductors such as metals allow electrons to flow through them, whereas insulators like plastics impede the flow of electrons.
what happens when two insulators are rubbed together?
friction causes electrons to move from one to the other and they become charged. the material that loses electrons becomes positively charged and the material that gains electrons becomes negatively charged.
can protons be transferred?
no, they are fixed in the nucleus.
draw the structure of an atom.
electrostatics : picture 1
why does a charged balloon stick to a wall?
electrostatics: picture 2
what does the nucleus of an atom contain?
protons and neutrons.
when does an atom have equal numbers of protons and neutrons?
when the atom is uncharged.
what is a charged atom called?
an ion.
name 4 examples of the uses of electrostatics.
- electrostatic paint spraying
- electrostatic smoke precipitator
- electrostatic crop spraying
- a photocopier
explain electrostatic paint spraying.
- the spray nozzle is connected to the negative terminal
- this makes all the paint droplets negatively charged.
- the paint droplets are sprayed from the spray nozzle and repel each other making them spread out.
- the metal being sprayed is connected to the positive or to an earth terminal, so the droplets are attracted to it.
- advantages to this are even coating and less mess.
explain the electrostatic smoke precipitator.
electrostatics: picture 3
- the smoke particles pass through the grid and pick up a negative charge.
- as the charged smoke particles move up trough the chimney, they are oppositely attracted to the charged plates and the grid is negatively charged.
- when the oppositely charges plates are covered with particles, they are tapped so that the particles fall to the bottom and can be cleared away.
explain electrostatic crop spraying.
electrostatics: picture 4
- if the insectide is given an electrostatic charge as it leaves the aircraft, then much more of the spray reaches its target and the spray droplets are spread out more evenly.
- the insectide droplets spread out more evenly because they all have the same charge and repel each other.
explain how the photocopier works.
- a rotating drum is given a positive charge.
- a light shines onto the paper to be copied, and the reflection falls on the drum.
- the drum is made of a special material that conducts when light falls on it, so the positive charge leaks away where the light falls.
- black powder that is negatively charged is sprayed across the drum (toner).
- the toner is attracted only to the charge area.
- a sheet of paper is passed over the drum.
- the toner is attracted only to the charge area.
- a sheet of paper is passed over the drum
- the toner is transferred to the paper, and is heated to fuse it to the paper.
give an example of charging by induction.
electrostatics: picture 5
what happens when a rod is rubbed with a cloth?
electrons are transferred from the rod onto the cloth and the rod becomes positively charged. the charges cannot move within the insulator so they build up- know as static electricity.
what are the dangers of static electricity?
lightning. electrostatic charge can build up on clouds due to friction. when the charge becomes large enough, the clouds discharge through the air to the earth. this results in lighting.
what is charging by induction?
a charging method which charges an object without actually touching the object to any other charged object. the charging by induction process is where the charging particle is held near an uncharged conductive material that is grounded on a neutrally charged material.
what do field lines look like around this magnet? is this a uniform magnetic field?
electrostatics: picture 6
what is the difference between a hard magnet and a soft magnet?
magnetically hard materials are substances that can be permanently magnetised (e.g. steel) and are hard to magnetise and demagnetise whereas magnetically soft materials are substances that can only be temporarily magnetised (e.g. iron) and are easily magnetised/ easily demagnetised.
explain the danger of refuelling vehicles.
fuel is an insulator and charge can be transferred as it flows through an insulating pipe. this happens because there is friction between the fuel and the pipe. when a nozzle is brought close to the fuel tank, a spark can jump between the two, igniting the fuel. this can cause a serious explosion. even if the car is discharge, charge can build up when fuel flows through the insulating pipe! the pipe nozzle is made to conduct by making it from conductive material or connecting an Earth strap to it. any charge can be safely conducted away.