Electricity Flashcards
Equation for current : current, charge and time
I= Q/t
Equation for voltage: voltage, electrical energy and charge
V= W/ Q
Ohms Law
Current and voltage are directly proportional
In a circuit was is used up and what is conserved between voltage and current
voltage is used up and current is conserved as well as charge
Conductor band width
Band gap between the valence band and conductor band is small. So many electrons travel through the conduction band
Semi Conductor band width
Band gap is larger so only few electrons reach the conduction band
Insulator band width
Does not conduct electricity so no electrons can reach the conduction band
Superconductors characteristics
Zero resistivity at and below the critical transition temperature (-260 degrees)
Equation for resistivity
resistivity= RA/ L
3 equations for power involving current, resistance and voltage
P= VI
P= I^2 R
P= V^2 / R
KIrchoff’s 1st law
At any junction in a circuit the sum of currents flowing in is equal to the sum of currents flowing out (conservation of charge)
Kirchoff’s 2nd law
For any closed loop in a circuit the sum of emf is equal to the sum of the potential difference (conservation of energy)
Examples of potential dividers
Thermistor
LDR
Variable resistor
Equation for potential energy of an electron
0.5mv^2
2 equations to calculate EMF
(r is internal resistance)
E= IR + Ir
E= I(R+r)
