# 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