Hello Guys I am a begginer in electronics and need a help in my first circuit. i am making a dark sensor and i used
Transistor BC547
LED
LDR
Resistor 150k ohms
Buzzer
Battery
I Want To Know Whats Problem In This Circuit Which I have Made.

 

What does or does it not do? Do you own a multimeter?

Need to know the characteristics of the LDR. Dark resistance? Resistance when illuminated? Data sheet?

Need to know the operating voltage and operating current of the buzzer? Data sheet?

Need to know the pin out of the BC547 relative to the flat on the package (can't tell from your photo)?

 

With a 150k resistor to +6V,th most current that could flow through the base of the transistor is 35 microamps; probably not enough. Try a lower value, maybe 20k.

What is the resistance of the LDR at the light level at which you want the transistor to turn on?

And while at it, what is the letter on the tarnsistor after "BC547"? That gives the current gain range.

 

Be sure that your "buzzer" is really a buzzer, and not just a piezo element. Does it buzz when connected directly to power and ground?

Also double check that you have correctly identified the emitter and collector on the transistor. Look at the datasheet for the transistor.