4.3 Electrical Circuits Flashcards
What is Kirchoff’s second law?
The total EMF across a circuit loop is equal to the sum of potential differences across devices in that loop
What does Kirchoff’s second law conserve?
Energy
What happens when cells are added in series? (2)
Current increases
Voltage increases
What happens when cells are added in parallel? (3)
Current stays the same
Voltage stays the same
Cells last longer
What happens when resistors are added in series? (3)
Voltage stays the same
Current decreases
R = R1 + R2
What happens when resistors are added in parallel? (3)
Voltage stays the same
Current increases
1 / R = (1 / R1) + (1 / R2)
Value of resistivity - conductors
In the order of 10^-8 ohm metres
Value of resistivity - insulator
In the order of 10^16 ohm metres
Value of resistivity - semiconductor
10^-8 to 10^16 ohm metres
What is internal resistance?
The resistance within a source of EMF, reducing the voltage supplied to the rest of the circuit (r)
What are lost volts?
The PD used on the internal resistance
What is the internal resistance equation?
E = V + Ir
E: EMF
V: terminal PD (available for use)
Ir: lost volts
What are the advantages of using a rheostat in a potential divider circuit? (2)
There is a full range of PD across resistor
Can be used to find IV characteristics
How are resistance and voltage divided in a potential divider circuit? (2)
R1:R2 = V1:V2
The PD across each component is proportional to its resistance
