Electricity Flashcards
Definition of electric current
rate of flow of charge
in which direction does current flow?
current always flows from positive to negative. electrons flow the opposite way
finding charge given number of electrons, passing through a point
Q = ne (Number of electrons times charge of one electron)
finding current given Number of charge carriers passing through a point per second
I = nQ (Number of charge carriers passing through per second times charge of each)
Kirchhoff’s first law
Electric charge is conserved in all circuits
Kirchhoff’s second law
Energy is conserved in all circuits. for any complete circuit loop, the sum of the EMFs is equal to the sum of the potential differences.
components of current, voltage and resistance throughout a circuit in series
components of current, voltage and resistance throughout a circuit in parallel
Ohm’s law
The potential difference across a conductor is proportional to the current through it, provided the physical conditions do not change
using a voltmeter
1) voltmeter must be connected in parallel with component (pd must be same for both)
2) current through voltmeter must be as small as possible (so pd across component not affected)(so voltmeters has very large resistance)
using an ammeter
1)ammeter must be connected in series with component (current must be same for both)
2) current through component must not be affected by ammeter. (So ammeters have very low resistance)
I-V graph for resistor
I-V Graph for filament lamp.
I-V Graph for semiconducting diode
variable resistor
a resistor whose value can be changed
graph of resistance agaist temperature for a thermistor
graph of resistance against light intensity for LDR
diode in forward bias
Emf of multiple cells
