Chapter 1. Basic Concepts Flashcards
What does charge measure?
counts the number of electrons (or positive charges) present
SI unit for charge
Coulomb, Q/q
What’s the difference between a capital variable and a lower case variable?
Capital = constant quantity
lowercase = variant quantity
One Coloumb is equal to
6.24 x 10^18
The movement of charges is called an
electric current
conventional direction of current flow is opposite to
direction of electron (negative charge) flow
Flows from positive terminal of battery
Electron flow flows towards
positive terminal of battery
Electric current (i) is described as… and is measured in…
change in charge over change in time, and measured in amperes
i = dq/dt
The charge transferred between t₀ and t will be…
Q(t) = ∫idt + Qt₀
integral has upper limit t
and lower limit t₀
What is voltage?
potential difference between two points
for Vab, what does a and b represent?
a = higher potential energy
b = lower potential energy
Power is described as…
the rate of energy provided per time
p = dw/dt
How do we calculate power?
p = vi = v²/R = i²R
When is power absorbed?
p = +vi
When current enters through the positive terminal and leaves through the negative terminal. (came with high energy and left with low energy)
When is power supplied?
p = -vi
When current enters through the negative terminal and leaves through the positive terminal. (came with low energy and left with high energy)
How does the law of conservation of energy apply to passive sign convention?
The sum of all power supplied must be absorbed by other elements
How are energy and power related?
w = ∫ p dt = ∫ vi dt
upper limit = t
lower limit = t₀
What are examples of active elements?
(generate energy)
Generators
Batteries
Operational Amplifiers
What are examples of passive elements?
(absorb energy)
Resistors
Capacitors
Inductors
How do we distinguish between dependent and independent sources?
independent = circle
dependent = diamond
What’s an ideal voltage source?
provides a specified voltage that is independent of other elements.
It has no internal resistance
What is internal resistance?
the opposition to the flow of current offered by the cells and batteries themselves resulting in the generation of heat.
What’s an ideal current source?
will generate any voltage to establish the desired current through them.
It has infinite internal resistance
