15 DC Flashcards
Resistance of an ideal voltmeter
An ideal voltmeter has infinite resistance.
Resistance of an ideal ammeter
An ideal ammeter has 0 resistance.
What is a galvanometer?
A sensitive ammeter that indicates direction of current flowing through it through the deflection of its needle.
Potential of earth
0 volts.
What is a transformer?
It is made up of 2 inductors wound around an iron core.
What is a capacitor?
A component that stores charge.
Definition of a series arrangement
Where the same current flows through the connected components.
Resistance of series arrangement
R = R1 + R2 + … + RN
R is always greater than any individual resistor.
R increases as more resistors are added in series.
Definition of a parallel arrangement
Where the same potential difference is set up across connected components.
Resistance of parallel arrangement
1/R = 1/R1 + 1/R2 + … + 1/RN
R is always smaller than any individual resistor.
R decreases are more resistors are added in parallel.
Steps for solving resistor network questions
1) Redraw circuit to simplify
Series: current completely flows through from one to another resistor.
Parallel: current at a junction splits up into 2 or more branches and merges after passing through resistors.
2) Short circuit connection
Isolate sections connected to the same junction (same potential)
Compare potential across electrical components.
Potential divider principle (series arrangement)
I = VT/R1 + … + RN = V1/R1 = VN/RN
Ratio of potential difference across resistors is equal to ratio of resistances.
