Lesson 1, Circuits Flashcards
Fundamental unit of charge
The electron, discovered by J.J Thompson 1897.
Relationship between charge and electrical field
Charge [ q ] interacts with an electric field [ E ] to generate a force F= qE ( electric field as the force per unit charge).
What is the difference between conductance and resistance?
Resistance [R] is the opposition to flow of electric current measured in ohms Ω.
Conductance [G] how easily electric current flows through a material. It’s reciprocal of resistance, measured in Siemens [S].
G= 1/ R
What is the difference between conductance and resistance?
Resistance [R] is the opposition to flow of electric current measured in ohms Ω.
Conductance [G] how easily electric current flows through a material. It’s reciprocal of resistance, measured in Siemens [S].
G= 1/ R
Principle of energy conservation in electrical circuits
Energy can’t be converted/ destroyed, only converted from one to another.
In a circuit, energy is drained from the source and dissipated as heat in resistors.
What is the definition of voltage
(Electrical potential difference) work done per unit charge to move a charge between two points in an electrical field.
How does electrical resistance arise in conductors
Resistance arises due to collisions between free electrons in the conductor and the atoms of the material- causing energy dissipation as heat.
What is the passive sign convention (PSC) in circuits
Current enters the positive terminal of a passive element (absorbing energy) and leaves the positive terminal of an active element (generating energy)
What happens when a charge moves through a resistor in a circuit?
The charge loses potential energy, which is dissipated as heat in the resistor, due to collisions between electrons and lattice ions.
Difference between ideal and real voltage sources
Ideal voltage: provides a constant voltage regardless of the load.
Real source: has an internal resistance, limits the current supply when connected to small circuit resistances.
Define electric drift
The rate of change of mobile charge in response to an applied E.
How to find the resistance R
R= ρL/ A, where A= wt
