night lamp

FSNSYou only learn by doing it yourself

From Scrap and Scratch

Experiment 1

Night Lamp

Materials Required

i. Bread Board

ii. Resistor: 220k ohm , 330 to 1000 ohm

iii. 9V Transistor Battery - 1

iv. Connecting Wire

v. LDR

vi. NPN transistor

vii. LED

Step 1

Take a Breadboard

Step No.2

Connect a 9V Battery on the breadboard

Step No.3

Connect a NPN transistor on the breadboard with its 3 pins( emitter base and collector) in 3 different holes

on the breadboard

Step No.4

Connect LDR between base of transistor and ground and connect emitter to ground

Step No.5

Connect a resistor of 220k ohm between base and Vcc(power supply)

Step No.6

Connect a combination of LED and a resistor between collector and Vcc. The LED doesn’t glow.

Step No.7

Now when we cover LDR with a black surface,LED glows

Reasoning

Covering the LDR increases the resistance and hence the potential at base increases thereby providing enough voltage to the base emitter junction to switch on.

An LDR as you must have studied in level 1 has resistance between 10 to 70k ohm. We are using this property of LDR to make our night lamp.

FSNSYou only learn by doing it yourself

From Scrap and Scratch