Power source

4. Power source Any electrical appliance or gadget

8. A + - Ammeter: A device calibrated in amperes and used to measure the intensity of an electric current. An ammeter must always be installed in series to measure the current. The current (I) is measured in amperes (A). Analogy to understand the ammeter: Now, imagine a river stream encounter a paddle wheel. The wheel is the ammeter and water is electric current.

13. An analogy: Let’s imagine a ball falling from different levels. Height difference or potential difference is high. Height difference or potential difference is low. Garfield

14. V + - Voltmeter: A device equipped with two terminals that indicates the potential difference (voltage) between these two points.. A voltmeter must always be installed in parallel to measure the potential difference. It measures energy in volts (V). Voltage: also termed potential difference which is a quantity related to the amount of energy that would be required to move an object from one place to another against various types of forces. e- B A An amount of energy is needed to move the electron from point A to point B. The difference in energy between A and B is called voltage.

19. A V 14 V or U (V) 12 10 8 6 4 + - I (A) 1 2 3 4 5 6 7 8 9

20. Calculating the slope of V vs. I : Resistance Current is a function of voltage: I = f (V) Slope = ΔV / ΔI = 4.0 V – 1.0 V / 8.0 A – 2.0 A = 3 V / 6 A = 0.5 Ω R = ΔV / ΔI R: Resistance (Ω) ΔI: Current (A) ΔV: Voltage (V) Hence: R = V / I V R I U (V) 6 5 4 3 2 1 1 2 3 4 5 6 7 8 I (A) R = ΔV = y2 – y1 ΔI x2 – x1

23. Ammeter Voltmeter

24. Resistors

34. + - + - Commonly used symbols in electric circuits: Power source Battery (Cell) Light bulb A Ammeter V Voltmeter Switch Push button switch Resistance Crossing wire with contact Crossing wire with no contact

37. ITotal = I1+ I2+ I3

39. VTotal = V1+ V2+ V3