P4 Flashcards
(35 cards)
What is electricity ?
It is a flow of electrons
How is static electricity crated give an example ?
Creating friction allows the transfer of electrons which causes static electricity for example if you rub a balloon on a jumper the jumper loses its negative electrons on to the ballon making the balloon negatively charged and the jumper positively charged so it will therefore stick to a wall as this would be neutral or positive the balloon would be attracted to it
What are the dangers of static electricity ?
Touching something with a large static charge causes an electric shook which can cause burns and even stop your heart
It is also dangerous when there is a flammable gas around as it can cause a spark and an explosion
When is static electricity a nuisance?
When dust and dirt are attracted to insulators such as TVs and get stuck to it .
Also clothes that have been in a tumble drier made of synthetic material cling together
How can you reduce the dangers of static electricity ?
Connecting an object that may become charged to an earth wire .
In a factory machine operators stand on insulating mats or wear insulating shoes preventing charge flowing through them
What is an electrostatic precipitator ?
They are fitted in factory chimneys to reduce smoke emissions .
It has a metal grid which is negatively charged and the smoke particles flow through this and pick up a negative charge this is charged by a high voltage the particles gain electrons .they are then attracted to positive collecting plates .
What is electrostatic spray ?
A spray gun is given a charge (negative) so the paint atoms gain electrons and become negative , the particles of the paint Repel against each other and spread out to make a fine spray , the object being planted is given the opposite charge (positive ) and the paint is attracted to it , the object gets an even coat and less is wasted
What is electrical resistance ?
An electric current flows when electrons move through a conductor ,such as wire the moving electrons can collide with metal ions making it more difficult for electrons to move through causing resistance
Does a thin or thick wire cause more resistance and why ?
A thin wire has more resistance as it has fewer electrons to carry the current and there is less room causing more collisions with metal ions
Does a long or short wire cause more resistance ?
Long wire has more resistance as the electrons have further to travel so have more chance of colliding with metal ions
How do you calculate resistance ?
Voltage ➗current
How does an alpha smoke detector work ?
Inside the smoke detector there is two charged plates and an alpha emitter (amercuim-241) the alpha particle pass through the two plates causing the air to ionise, ions are attracted to oppositely charged plates causing current to flow , the chamber has vents that allow smoke to enter , when it does enter the alpha particles are absorbed causing less ionisation and a smaller current to go through therefore the alarm is sounded
What is most background radiation from ?
Radioactive substances in soil and cosmic rays from space also medical equipment
How can a radioactive detector be used to find a crack one blockage in a pipe ?
Gamma rays are emitted into the pipe and a tracer picked up levels of the radiation, if there is a leak more radiation will be detected and if their is a blockage the radiation will stop flowing as much so won’t be detected as much
What is carbon dating ?
Living materials contain a certain amount of carbon and when they die the carbon-14 begins to decay as they can no longer exchange gases , the carbon-14 in the atmosphere has remained unchanged for years therefore scientists can tell how old something is by the amount of carbon-14 is left in it
What is half-life ?
Half-life is the time taken for half of the radioactive nuclei to decay
E.g. 1000units - 500units the time taken for this to happen is a half-life
What happens to the radioactive particles when it decays (half-life) ?
Every half-life a radioactive substance loses half of its radioactive particle these are just replaced with another atom until there is no radioactivity left which can take millions of years
What is the relative mass and charge of a proton , neutron and an electron ?
Proton - relative atomic mass of 1 and a positive charge
Neutron - relative atomic mass of 1 and a neutral charge
Electron - relative atomic mass of 0.0005 and a negative charge
What is an isotope ?
An isotope is a different version of an element /atom it will have the same atomic number but a different atomic mass therefore it will have more protons or neutrons than the original for example carbon has an atomic mass of 12 and an atomic number of 6 , an isotope of carbon is carbon-14
What is beta decay ?
Carbon-14 is radioactive if it undergoes beta decay it becomes
-6 Nitrogen -14
-7. As a neutron turns into a proton and an electron , the electron shoots out of the nucleus and becomes a beta particle
Carbon-14 ➡️ nitrogen-14 (7) ➕ e - / B -1
What is alpha decay ?
The radioactive substance that undergoes alpha decay loses 2 protons and 2 neutrons for example :
U-238(92) ➡️Th-234(90) ➕He-4(2)/A
What is a fuse and how does it work ?
It is a safety devise to prevent fire 🔥 it’s designed to break a circuit if a fault occurs
It is a short, thin wire with a low melting point
How does the fuse work within the plug ?
Of a fault occurs inside an appliance , the live wire will make contact with the neutral wire , the current will be higher than the fuse due to the low resistance so the fuse wire will get hot and melt causing the circuit to break therefore the current is unable to flow so no danger of fire 🔥
What does the live wire , the neural,and the earth wire do ?
The live wire - carries the high current to the appliance
The earth wire - it is a safety wire preventing the appliance becoming live
The neutral wire- completes the circuit and carries current away from device
