little confusion in analog stuffs

[Bhuvanesh123]

void setup()
{
  Serial.begin(9600);
 }
void loop()
{
  int a= analogRead(3);
  Serial.println(a);
  delay(1000);
}

but i have not connected anything to that analog pin but i am getting values around 500.whats the reason for that

 

[barry]

My mind-reading skills have failed me, I am unable to determine what you are talking about. Perhaps a microprocessor? Maybe a spaceship? And your circuit? Maybe it's a modulated neutrino-beam device or an automatic tomato picker?

If you expect someone to help you, show a minimum amount of effort by posting an intelligent question. Don't throw up 5 lines of code and expect the world to know what you're talking about.

 

[godfreyl]

but i have not connected anything to that analog pin but i am getting values around 500.whats the reason for that

If there's nothing connected to the input pin, then it's voltage is random/undefined.

If you want the voltage on that pin to be 0V, then connect it to 0V.

 

[electronicsensation]

seems to me as you are working on arduino.... if analog pin is floating then it will pick interference, feed known voltage into this pin and verify values.