PEOPLE AND MONEY
People represent moving charge. Money represents energy transferred. Spending money does not remove people from the route.
Voltage measures energy transferred per unit of charge. Current measures the flow of charge.
PEOPLE, MONEY & CIRCUITS
People leave home with money and spend it at stores. Nobody joins or leaves the trip. They must spend all their money before they return home.
I is the number of people.
V is money per person.
- ONE STORE
- TWO STORES
- TWO PATHS
GUIDE COMPLETE
OHM'S LAW
V = I × R
V is the voltage spent at a resistor, I is the current through it, and R is its resistance. All three values describe the same resistor. V is not automatically the battery voltage.
SERIES
The same current passes through each resistor. Adding the voltage spent at each resistor gives the battery’s voltage.
Rtotal = R1 + R2
PARALLEL
The paths begin and end at the same two points, so the same voltage is spent on each path. Different resistances can give different currents.
Itotal = I1 + I2
On each path, I = V / R. Adding the currents and dividing by the voltage spent on each path gives:
1 / Rtotal = 1 / R1 + 1 / R2
KIRCHHOFF'S LAWS
At a junction, the current entering equals the current leaving. Everyone is accounted for.
Around a complete loop, the voltage supplied by the battery equals the voltage spent at the resistors. In these circuits, each person receives money at home and spends it all before returning.