new electricity Flashcards
what is current
rate of flow of charge measure in amps ]
what is charge and current and time formula
charge = current x time
charge carriers in
an insulator
metallic conductor
semiconductor
in an insulator electron is attached to an atom and cannot move away from the atom when supplied with a volatge current is 0 because no electron can move
metallic conductor most electrons are attached to atoms but some are delocalised meaning when supplied with a volatge they act as the carrier and are attrated towards positive terminal
in a semiconductor the number of charge increase with temperature and reissitance decreases with temperature
define potential difference
workdone per unit charge
formula for electrical power and current ( workdone)
w = I x V x T
what is ohms law
pd across a metallic conductor is proportional to the current through it provided that the physical conditions do not change
what is a superconductor
superconductor is a wire or device made of materials that have 0 resistance at and below a critical temperature
superconductor advantages and disadvantages
very expensive and need to be kept at low temperature
advantages
can be used in MRI scanners and in developing new applications such as lightweight electron motors and cables that transfer energy without energy dissipation
9 shows a practical circuit in which a variable resistor is used to control the
brightness of a lamp. The voltmeter reading is monitored as the variable resistor is
adjusted to make the lamp brighter.
Explain why the reading on the voltmeter decreases as the brightness of the lamp
increases. ( doesnt say in question that battery has negligible internal reisitance
current increases
volts lost due to internal resistance also increases therefore terminal pd decreases
what can superconductors be used for
to produce strong magnetic field
cells are in parallel what is total emf
would take emf of one cell
what is potential difference
two or more resistors in series
