Voltage, Current and Resistance

Voltage, Current and Resistance

1. Series Circuit

   • Voltage
     • Shared across all components
     • V = V1 + V2
     • Voltage around always adds up to voltage across the battery
       • Total work done on charge by battery = total work done by charge on components
     • Adding a cell
       • Cell voltages add up
         • C = C1+ C2
   • Current
     • The same everywhere
       • All components get the same current
     • A1 = A2 = A3
     • Size is determined by total voltage of the cells and resistance of the circuit
     • Adding cells
       • Increases voltage but not resistance
         • Current increases
   • Resistance
     • Sum of resistances of all components
     • R = R1 R2
     • The lager the resistance, the larger the share of voltage the component receives

2. Parallel Circuit

   • Voltage
     • P.D is the same across all components
       • Each component = P.D of battery
     • V1 = V2 = V3
     • Identical bulbs in parallel will be same brightness
     • Adding cells
       • Total voltage stays the same
         • Each charge only goes through one cell
         • C = C1 =C2
   • Current
     • Adding cells
       • Increase total current
         • Current through each cell is less than the rest of the circuit as they join to make the total current
     • Total current is shared between braches
       • A = A1 + A2
       • Current into junction = current leaving
   • Resistance
     • Always less than that of the branch of the lowest resistance
       • Charge has more than 1 option, so only some flows across each branch
       • Circuit with 2 resistors in parallel < resistance than circuit with resistor alone
         • Parallel has higher current

3. Types of Current

   • AC
     • Alternating current
     • Our mains supply
     • Allows transformers to work
     • Easy to generate/ transport
       • Turn a magnet inside an iron core!
   • DC
     • Direct current
     • In batteries
     • Harder to generate/ transport than AC