Chapter 2: Sensing Flashcards
What is an electric current?
The flow of charged particles.
What is the equation for the current of an electron/ion beam?
I=nq
current = no of particles per second x charge of particle
what is the equation for electric current (and charge and time)?
Q=It
charge = current x time
equation for p.d. (given charge and energy)
V=E/Q
p.d. = potential energy difference / charge
equation for p.d. (given current and resistance)
V = IR (pd = current x resistance)
three equations for power
P=IV=I^2R=V^2/R
What is conductance?
the current for a given pd
equation for conductance
G = I/V
what is resistance?
The pd required for a given current
equation for resistance
R = V/I
relation between conductance and resistance?
G=1/R ; R=1/G
They are reciprocal quantities
State Ohm’s Law
For an ohmic conductor, in constant external conditions, V=IR
Is a filament lamp ohmic? Why?
NO!!! Because its temperature does not remain constant! I/V graph looks like an “f”
What is a diode?
A semiconducting component which only allows current to flow in one direction.
What adds up in series?
Resistances and voltages
What adds up in parallel?
Conductances and currents
What is emf? (1 - relating to charge)
Electromotive force - the electrical energy supplied to each charge by the chemical reaction in the battery.
What is emf (2 - relating to current)
The terminal voltage when there is no current drawn.
emf equations:
V = e - Ir = e - v e = I(R+r) = V + v
What is the potential divider equation?
V_1 = V_c x (R_1/R_1+R_2)
What is internal resistance?
The resistance to electrical current by the atoms in the cell.
What is Kirchoff’s First Law?
The total current entering a junction is equal to the total current leaving a junction.
What is Kirchoff’s Second Law?
The total emf around a series circuit is equal to the the sum of the potential differences across each component.
