Bmat section 2 physics Flashcards
Describe how insulators like a cloth and a plastic rod can be charged by friction. and what is this process known as, why does it have this name
If a plastic rod and a cloth are rubbed against each other, one of the two will lose electrons to the other. If the rod loses electrons to the cloth, it will have less electrons and therefore will be positively charged, and the cloth will be negatively charged as it will have more electrons. This is called static electricity. it is static because, the electrons cannot move in the cloth/ rod as they are insulators, so we can say that the insulators “HOLD” the electrons
hazards of static electricity
it can cause a spark which can be dangerous
an example is when an aircraft is being refueled.
lightning is also a hazard of electrostatics
how is sparkling in static electricity prevented
by earthing
in the example of the refueling of an aircraft, both the aircraft and the truck are earthed and this prevents any charges from building up and leading to a spark
unit for charge
coulombs
conservation of charge rule
charge can be conserved but cannot be created nor destroyed
can positive charges move in solids? give a reason for your answer
no they can’t, because they are held in place by other atoms.
effect of distance on electrostatic forces between charged objects
As the distance between charged objects increase, the electrostatic force between the objects decrease (become weaker) and vice-versa
applications or uses of electrostatics
can be used in photocopier machines
can be used in laser printers
can be used in electrostatic spray painting
what happens when a live wire touches a metal casing that has been earthed
a large current will flow to the Earth and
blow the fuse, disconnecting the appliance from the power supply.
This protects users from electric shock. This also protects the wiring of the
circuit from overheating and causing a fire
types of current and their definitions
Direct current: in direct current, the flow of electric charge is in only one direction
Alternating current: in this type of current, the flow of electric charge periodically reverses direction
conductors and insulators, their definitions and examples
conductors are materials that permit electrons to flow freely from particle to particle. examples are metals, the human body, aqueous solutions…
inductors are materials that impede the free flow of electrons from atom to atom
and molecule to molecule. examples are plastics, paper, and dry air.
formula for current
charge/time
formular for resistance
voltage/current
formula for voltage(linking energy and time)
energy/time
formula for power(linking current and voltage)
current* voltage
the formula for energy transfer
power*time
the rule for current in a parallel circuit
the current in the branches of a parallel circuit add up to the total current leaving the cell
the rule for current in a series circuit
the current is the same all around the series circuit
what does the potential difference (voltage) tell us
the amount of energy transferred for each coulomb of charge moving through an electrical circuit
voltage in a series circuit
the voltage is the same across a series circuit, however, when they are more than one appliances, then the potential difference is shared between the appliances
potential difference in parallel circuits
for components connected in parallel, the potential difference across each component is the same as the potential difference of the cell
ELECTROMOTIVE FORCE equation
POWER/CURRENT
when can we say an ammeter has zero error
when an ammeter displays a reading while not connected to a circuit
Which waves transfer the most energy
Waves with the short wavelength and high frequency