Triple Electricity: Static Electricity + something about charge Flashcards
What is electric charge?
Electric charge is given energy by the battery/power supply, and as it flows around a circuit it converts the energy into other forms in components such as light bulbs, motors etc. Charge can be thought of as an ‘energy carrier’
What is voltage?
The number of joules of energy transferred - given to the charge in the case of a battery/power supply; given up by the charge in the case of resistors, etc - as one coulomb of charge passes through a component is equal to the voltage, or potential difference, across it
What is 1 volt equal to?
1V = 1J/C
What is the equation between voltage, energy and charge
voltage = energy / charge
What is electric current?
The flow of charge
What happens when two insulating materials are charged by friction?
When two insulating materials (e.g. a polythene rod and a cotton cloth) are rubbed together, they both obtain an electrostatic charge. What has happened is that the electrons have been transferred from the cloth to the rod (outer electrons are easy to remove). This leaves the rod negatively charged (i.e. with more electrons than it should have) and the cloth positively charged (i.e. with fewer electrons than it should have
Why does the electrostatic effect not work on conducting materials?
Because any charges that are produced are quickly conducted away
What is an important thing to note about the protons?
It is always the electrons that move about - the protons are locked deep down inside the nucleus and cannot jump about or be transferred
Give examples of substances that become positively charged when rubbed
Cellulose acetate, glass, wool silk, cotton cloth
Give examples of substances that become negatively charged when rubbed
Amber, rubber (e.g. balloons), polythene
What is the triboelectric series?
Something that ranks the tendency of materials to gain or lose electrons from the electrostatic effect
What are the forces between like charges and unlike charges?
Like charges repel
Unlike charges attract
Explain what happens when an uncharged conducting object (e.g. a metal sphere hanging from an insulating wire) touches a charged insulating material (e.g. a negatively charged polythene rod)
If the rod touches the metal sphere, some of the electrons on the rod will move onto the sphere making it negatively charged too.
(The same thing happens if the sphere is connected to the negative terminal of an extra high tension (EHT) power supply i.e. one that can produce potential differences of several thousand volts - or to the negatively charged dome of the Van de Graaff generator)
Explain what happens when a charged insulating material (e.g. a negatively charged polythene rod) is held close to an uncharged conducting object (e.g. a metal sphere hanging from an insulating wire)
If the rod is held close to the metal sphere, electrons on it are repelled to the far side, leaving the side closest to the rod positively charged. The sphere is now said to have (temporary) induced charges
However if the sphere is now earthed (e.g. by touching it), electrons in the sphere will take the opportunity to get even further away from the rod by flowing down into the Earth. If the connection is then removed, the sphere will be left with a permanent positive charge - as the electrons will not be able to return to it.
This process is called charging by induction.
* The charged produced is opposite to that on the object that does the inducing (the rod)
Explain how uncharged small particles (e.g. pieces of paper) can be attracted to a charged rod
When you rub together the two insulators, electrons are transferred so there are extra electrons on the rod, meaning it has a negative charge
When the small, neutral particle is near the rod, some electrons move away from the rod to the other side of the particle because of the high amount of electrons on the rod
This leaves more protons on on the side of the particle near the rod so there is a positive charge on that side. This creates a force of attraction between the negative charge on the rod and the positive charge on the particle