Kirchoff's Laws

We started off class by reviewing Kirchoff's Current Law and Voltage Law in series and parallel circuits.

Kirchoff's Current Law

• The current is conserved in a series circuit. It is the same throughout the circuit. I1=I2=I3=IT.


• The total current in a parallel circuit is the sum of the current through each resistor connected in parallel. I1+I2+I3=IT

Kirchoffs Voltage Law

• In a series circuit, th total (Vt) is the sum of the potential difference across each individual resistor connected in series. V1+V2+V3=VT


• In a parallel circuit, the voltage is conserved. The potential drop across each resistor in a parallel is equal to the total voltage. V1=V2=V3=VT

Then we did book questions Page 646#1-4

After that we looked at Electrical Rsistance. Electrical resistance is the amount of current drawn from an electrical energy source depends on the internal resistance of the appliance that is "plugged in" and where R=P(L/A)

R=resistance

P=resistivity

L=length

A=cross-sectional Area

We also looked over Ohm's Law V=IR

• If the voltage is constant , an increase in curent(I) must be the result of a decrease of resistance


• If the resistance is constant, an increase in voltage results in a directly proportional increase in current.

Resistors in Series

The total restistance is equal to the sum of individual resistor on series

Rs=R1+R2+R3+..+Rn

Resistors in Parallel

The total resistance is a reciprocal relatonship.

1/Rp=1/R1+1/R2+...+1/Rn

As more resistors are added, the total resistance becomes less. Therefore, the total current will increase