Electricty 2 Flashcards
(17 cards)
How would you find the resistance on an IV Graph of an ohmic conductor?
Find the gradient
If it’s not an oh,if conductor how would you find the resistance of a line an IV graph?
Using the equation R = IV
Define internal energy?
Of a body is the sum of the potential energy and the kinetic energy of its molecules
Define resistivity
(Rho ) it’s a property of a material and is defined by the equation R = rho l / A
-units are ohms m
Longer wire makes it more difficult for …………
Electrons to flow
Large cross sectional areas make it easier for…
Electrons to flow
What causes resistance?
Vibrating positive ions in the crystal lattice of the metal making it harder for electrons to flow
Positive temperature coefficient
Is when it’s resistivity increases when the temperature increases
In a thermistor the resistivity ……… with the temperature
Decreases
Negative temperature coefficient
Resistivity decreases when its temperature increases
What happens if the temperature gets too high in an insulator?
The insulator will begging to conduct as the energy from the heat breaks down the atomic structure so charge carriers are realised
What’s conservation of energy?
Energy can’t be created or destroyed but merely changed from 1 form to another
What’s internal resistance?
Of a cell it opposes the flow of charge through the cell
-some of the energy converted by the cell will be used inside the cell to overcome this resistance
What are lost volts ?
The energy wasted per colour overcoming the internal resistance
What happens when the temperature increases in the thermistor?
The R will decrease so V will increase
Put emf, R, r and I in a formula?
Emf = I (R+r)
Put V, emf, I and r in an equation?
V = emf -Ir
