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Starting electronics<br />

ting diode) connect to the more positive side in the circuit.<br />

A breadboard layout is shown in Figure 6.4, though by this<br />

stage you should perhaps be confidently planning your own<br />

breadboard layouts.<br />

Figure 6.4 A breadboard layout for the circuit in Figure 6.3<br />

Which way round?<br />

If you’ve connected the circuit up correctly, the LED should<br />

now be on. This proves that current is flowing. To calculate<br />

exactly what current we can use Ohm’s law. Let’s assume<br />

that the total battery voltage of 9 V is dropped across the<br />

resistor and that no voltage occurs across the two diodes. In<br />

fact, there is voltage across the diodes, but we needn’t worry<br />

about it yet, as it is only a small amount. We’ll measure it,<br />

however, soon.<br />

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