1.Two stage common emitter amplifier does not create 20 mili volts or more than 20 mili volts. It is not sufficient to convert electrical energy in digital form.analog to digital converter requires at least 20mili volts to work.

2. Resistance is inversely proportional to current and voltage.

3.Each variation of output of analog to digital converter have 20 mili volts, therefore the total output voltage is approximately equal to 5 volts.

4.Diode requires at least 0.7 volts cross the diode to work.

5.Voltage across the base is equal to 0.7 volts + (Resistance) (capacitance). 

6.There is single analog signal at pin no. 26 by using 000 at pin no. 23, 24, 25 (ADC 0808). It doesn't require other port. 

7.Monostable does not create frequency, buzzer creates frequency due to internal oscillator.

8.Current is directly proportional to reactance (resistance of capacitor ).

9.As we reduce the flow of energy, the efficiency of the circuit increases. 

10.Transistor goes on saturation mode when current across it increases and resistance across it decreases.

11.The capacitor discharges through the resistor connected across it. As we increase across value, the time required to discharge the capacitor increases. Here (Resistance) X (Capacitor) = Time.

12.When we trigger the monostable circuit, it's Tmark time becomes 1.1 (Resistance) (Capacitance).

13.Fourth LED is the limit.

14. Our gadget is useful because it can be used as a reference point by students to know how much noise they are creating.