p3 - electricity (from textbook) Flashcards
what happens when you rub two insulators together?
you can transfer electrons from one insulator to the other
describe how to discharge an object
connect it to something that allows the charges to flow e.g. cobalt
define current
the rate of flow of charged particles, or charge
define conventional current
positive to negative flowing current
what is conventional current the opposite of?
electron flow
define potential difference
the difference of electrical potential between two points
describe a series circuit
a circuit with only one loop
describe a parallel circuit
a circuit with 2 or more loops
describe current in a parallel circuit
it adds up
describe the resistance in a parallel circuit
always smaller than the smallest resistor
describe the resistance in a series circuit
it adds up
describe how resistance is produced
when delocalised electrons collide with other ions in the lattice
define a characteristic graph
a graph of current against potential difference
describe ohm’s law
the current is proportional to the p.d if the temperature does not change
name and describe an example of a non-linear circuit element
a wire in a light bulb - electrons collide with ions, but as the wire heats up, they move faster and more collisions happen - current increases at a slower rate compared to the potential difference
describe a diode
a component that only allows a current to flow one way
describe the characteristic graph of a diode
0 current for ages, then the current suddenly increases
describe a thermistor
a component made from a semiconducting material, where its resistance depends on temperature
describe the most important characteristic of a semiconductor (according to physicists)
electrons in the atoms of a semiconductor do not need much energy to escape from the atom to form the current
describe how a thermistor works
as you heat it up, electrons gain the energy to escape from atoms in the semiconductor
describe the main characteristic of a LDR and how it works
its resistance changes with light intensity - light cause electrons to be released into the circuit to increase the current
name and describe a potential use for a thermistor
could be used in a sensing circuit to produce a potential difference that changes with temperature - could use it in a heater or air conditioning
describe the difference between a cell and a battery
a cell is a single unit that produces electricity, whereas a battery is a group of cells connected in series and/or parallel
