3.2 Static Electricity Flashcards
What is Coulomb’s law used for
Used to calculate the force of attraction between two particles
What makes metals good conductors
Sea of delocalised electrons.
Electrons free to move therefore carry charge
Is water a conductor or an insulator
Pure water is a good insulator.
However if the water contains impurities then it will conduct electricity easily
What happens when you pass a current through pure water
The electric current decomposes the water, producing hydrogen and oxygen gas.
The hydrogen forms at the cathode, oxygen forms at the anode.
What is an “electron cascade”?
Once a few electrons are split from a few atoms they reach very high speeds due to the low pressure and high potential difference.
They collide with atoms which ionises the atom, producing several more electrons which also accelerate.
This process repeats itself producing lots of free electrons and positive ions.
Describe static charge by use of induction
Bringing a positively charged rod near a body, draws the body’s electrons towards the positive rod. Thus redistributing the charges within the bar so that one end of the bar is positive and one end is negative.
Touching the body at the other end with an earthed object will draw the electrons off the finger and into the body, leaving it with an overall excess of electrons.
State Coulomb’s law
The electrostatic force is directly proportional to the product of the magnitudes of the charges, and inversely proportional to the square of the distance between them
State Coulomb’s law
The electrostatic force is directly proportional to the product of the magnitudes of the charges, and inversely proportional to the square of the distance between them
Unit of charge and its measurements.
Q.
Coulombs
Explain conduction in a solid
When an electron enters a conductor, another electron is pushed out at the opposite end. Called a current.
Formula for Coulomb’s law?
F= (k x Q1 x Q2) / d^2
K = 9.0 x10^9 Nm^2/C^2
Conduction in solids
Applying electrostatic force causes electrons to flow from the negative to the positive pole.
What happens when a conductor narrows?
Where current is constant the electrons must move much faster, leading to heat and light produced
Current in a gas
Electron cascade happens which ionises the atoms
Eventually some atoms ant electrons recombine which releases light and energy
Some of the electrons and reach the ends of the tube, carrying their charge meaning a current can flow
What is a fluorescent tube used for
Absorbs electromagnetic radiation from a gas discharge chamber and re-emits it in a broad spectrum of visible light, making it a source of white light
