SI Units and Definitions Flashcards
What is the Unit Name and Formula of Frequency?
Symbol: f
Unit Name: Hertz(Hz)
Formula: Hz = s-1
What is the Unit Name and Formula of Force?
Symbol: F
Unit Name: newton(N)
Formula: N = kg*m/s2
What is the Unit Name and Formula of Energy/Work?
Symbol: w
Unit Name: Joule(J)
Formula: J = N*m
What is the Unit Name and Formula of Power?
Symbol: P Unit Name: watt(W) Formula: P = J/s
What is the Symbol,Unit Name and Formula of Electric Charge?
Symbol: q
Unit Name: coulomb(C)
Formula: q = A*s
What is the Unit Name and Formula of Electric Current?
Symbol: i
Unit Name: ampere(A)
Formula: N/A
What is the Unit Name and Formula of Electric Potential?
Symbol: V
Unit Name: volt(V)
Formula: V = J/C
What is the Unit Name and Formula of Electric Resistance?
Symbol: R
Unit Name: ohm(Ω)
Formula: Ω = V/A
What is the Unit Name and Formula of Electric Conductance?
Symbol: G
Unit Name: siemans(S)
Formula: S = A/V
What is the Unit Name and Formula of Electric Capacitance?
Symbol:
Unit Name: farad(F)
Formula: F = C/V
What is the Unit Name and Formula of Magnetic Flux?
Symbol:
Unit Name: weber(Wb)
Formula: Wb = V*s
What is the Unit Name and Formula of Inductance?
Symbol: Unit Name: henry(H) Formula: H = wb/A
Current is repesented by I, what is the difference between the lowercase ‘i’ and uppercase ‘I’?
- Lowercase “i” represents the instantaneous value of a changing current (it might be sinusoidal or switching on and off, for example).
- Uppercase “I” represents a steady current that is not changing value.
Charge is represented by Q, What is the difference between lowercase’q’ and uppercase ‘Q’?
- ‘q’ is the symbol for the instantaneous value of charge
- ‘Q’ for a static charge value
What is the nature of potential energy?
Potential relates to the capacity to do work.
You can only have potential in a given state **with respect to **some other state.
How do we work out what power is positive
and negative on a circuit diagram?
The diagrams mean that power = +ve whenever the direction of the current is drawn in the same ‘direction’ as the reference voltage drop.
That is, we first look at the voltage reference and imagine the direction that the current ‘should’ flow. And if the drawn arrow is in the opposite direction to the ‘conventional’ direction, then we just write p = -v.i
Dissipated energy is considered positive.
What is an idependent potential source?
(ideal voltage source)
An ideal voltage source is a circuit element that maintains a prescribed voltage across its terminals regardless of the current flowing in those terminals.
NOTE: Ideal circuit elements do not exist as practical devices - they are idealized models of actual voltage and current sources.
What is an independent current source?
(ideal current source)
An ideal current source is a circuit element that maintains a prescribed current through its terminals regardless of the voltage across those terminals.
What are dependent current and voltage sources?
A dependent voltage/current source is a circuit element where the voltage/current of the source is dependent on another parameter (voltage or current from another part of the circuit).
Standardized Prefixes
