I NTRODUCTORY DISCUSSION ON O HM ’ S L AW Ohm’s law quantitatively: as voltage increases, current increases if resistance is constant. Equipment required; 3 off penlight cells (AA) in holders 1 off 1ohm 20 watt* resistor (Brown, black, red and gold bands) 2 off multimeters * Called for by CAPS ELECTRICAL / ELECTRONIC SYSTEMS TECHNOLOGY Grade 9 Term 3 Presenter: Jan Randewijk 29 August 2013

Measuring Current Identify the section, labeled “DCA“ on the multimeter Connect the red test lead to the “V mA” terminal, (if the current to be measured is between 200 mA and 10 A, connect the Red test lead to the “10 A” terminal) and the black test lead to the “COM” terminal. Adjust the range selector to the “A” region. If measuring an unknown current, start from the highest range, then adjust to a proper lower range for the best resolution. Connect the other ends of the test leads in series with the part of the circuit where the current is to be measured. (Disconnect the circuit and place meter in series) The current value is then read from the display.

Measuring DC voltage Identify the section, labeled “DCV“ on the multimeter Connect the red test lead to the “VΩ mA” terminal, and the black test lead to the “COM” terminal. Adjust the range selector to the “DCV ”. Set meter on highest range Connect the other ends of the test leads parallel across the part of the circuit where the voltage is to be measured. (red test lead to +, and black test lead to -) The voltage reading is then read from the display, adjust voltage selector until a good reading is displayed. (In full numbers not in decimals.)

In a recent article in the “WEGRY September 2013” penlight cells were tested. A 6Volt 0,3A lamp was connected across various batteries consisting of 4 penlights. Criteria Duracell Plus Eveready Power Plus Silver Energizer Advance Period the lamp remained “ON” 5hr 20min1hr 45min4hr 24min Cost of a cellR14.99R5.65R16.99 Cost in cents/min4,68 cent5,38 cent6,44 cent Rating calculated by JR 1590mAh525mAh1296mAh

I NVESTIGATION O HM ’ S L AW Ohm’s law quantitatively: as voltage increases, current increases if resistance is constant. From our discussion it is clear that we cannot use a 1Ohm resistor, and as the rating of penlight cells are mAh, we propose to use a 1k-ohm resistor. Equipment required; 3 off penlight cells (AA) in holders 1 off 1000 ohm 1 watt resistor (Brown, black, red and gold bands) 2 off multimeters

Procedure Construct a circuit in figure 1.24, use a cell, resistor and ammeter (use multimeter set on Ampere scale) in series. Figure 1.24: Circuit with one cell, resistor and ammeter.