| Therefore
we can work out the voltage across the LDR:
Remember that 10 milliamps = 0.01 amp. V = IR = 0.01 A × 100 ohms = 1 volt. Therefore we can say that the voltage across the series resistor is 20 - 1 = 19 volt So we now work out the resistance with R = V/I = 19 volts ÷ 0.01 = 1900 ohms. |