user68988: I was just learning about I2C between 2 Arduinos, one as sender and another as a receiver
So I have got curiosity to know how many Arduinos can be connected to I2C connection in serial?
I mean,
Arduino1 --> Arduino2
Then can I connect Arduino3 to
Arduino 2 then again Arduino 4 to Arduino 3? Till how many Arduinos can I continue this connection?

user14095: The number is as many as you want.  There are switches that allow you to select different busses and each buss supports its full complement. From my point you are trying to use a solution before you have defined the problem fully. I have a feeling they will not be within a few inches of each other so consider an alternative designed for this type of use. CAN, RS485 and other interfaces would work much better with a lot less effort on your part.

user4143: The limiting factor is the bus capacitance. This is the limit of the total capacitance of the bus from all devices connected to it plus the capacitance of the wires used.
It is also affected by the value of the pullup resistors.
The limit, according to the specifications, is 400pF.  An Arduino has an input capacitance of 10pF.  So ignoring the wires that's an absolute limit of 40 Arduinos all connected together.
Reduce that a bit for the wires, so say 30 is a reasonable estimate. Then reduce that again if you're using the internal pullups which are about 10x bigger than they should be. That gives you a guestimate of 5-10 devices.
Use proper pullups instead of the internal ones (why oh why oh why did Arduino ever encourage and even make default such a stupid option?!?!?!) of say 1kΩ and keep wires very short and you'll probably be OK up to 20-25 devices.

68988: <p>I was just learning about I2C between 2 Arduinos, one as sender and another as a receiver</p>
<p>So I have got curiosity to know how many Arduinos can be connected to I2C connection in serial?</p>
<p>I mean,</p>
<p>Arduino1 --&gt; Arduino2</p>
<p>Then can I connect Arduino3 to
Arduino 2 then again Arduino 4 to Arduino 3? Till how many Arduinos can I continue this connection?</p>
 14095: <p>The number is as many as you want.  There are switches that allow you to select different busses and each buss supports its full complement. From my point you are trying to use a solution before you have defined the problem fully. I have a feeling they will not be within a few inches of each other so consider an alternative designed for this type of use. CAN, RS485 and other interfaces would work much better with a lot less effort on your part.</p>
 4143: <p>The limiting factor is the <em>bus capacitance</em>. This is the limit of the total capacitance of the bus from all devices connected to it plus the capacitance of the wires used.</p>
<p>It is also affected by the value of the pullup resistors.</p>
<p>The limit, according to the specifications, is 400pF.  An Arduino has an input capacitance of 10pF.  So ignoring the wires that's an absolute limit of 40 Arduinos all connected together.</p>
<p>Reduce that a bit for the wires, so say 30 is a reasonable estimate. Then reduce that again if you're using the internal pullups which are about 10x bigger than they should be. That gives you a guestimate of 5-10 devices.</p>
<p>Use proper pullups instead of the internal ones (why oh why oh why did Arduino ever encourage and even make default such a stupid option?!?!?!) of say 1kΩ and keep wires very short and you'll probably be OK up to 20-25 devices.</p>
