Ohms law/ resistance

• The only circuit you'll ever need = ohms law circuit
• resistance is measured by: current= Voltage / resistance
• Resistance of a circuit with resistor 1 (4 ohms) + resistor 2 (6 ohms) = 10 ohms resistance
• To find resistance of a series circuit (if given resistor ohms) just add
• total resistance for parallel = (1/r1 + 1/r2)^-1
• Cheat method for finding resistance (only if 2 resistors!!): r1 x r2/r1+r2
• resistance of parallel circuit (r1=12;r2=4)= 12x4/12+4= 3 ohms
• ohms law states: voltage is directly proportional to current (if we double v, I is doubled) IF R STAYS CURRENT!
• Ohms law states: if we push something twice as hard, it will move twice as fast (e.g a person pushed by 2 people will move faster than just one) IF THE R STAYS CONSTANT
• a bulb doesn't follow ohms law = bulb gets hot, resistance increases, blocking current. Hotter it is = more wasted current
• total r in a parallel circuit = 1/r1 + 1/r2
• power = current^2 x resistance
• steeper the line on the graph, lower the resistance, but more power used
• practical =

  • set up circuit identical to diagram
  • use variable resistor to increase the V shown on the voltmeter by 1V and record current
  • repeat for 2-10V recording current for each
  • Draw a graph where y=current and x=voltage
• less steep the line = more resistance as there is less current being used