I have doubt about the connection of resistance. In this why can’t we use less or more than the 10kohms resistor. This is the only doubt until I learned.
The use of the resister kept in series with the LDR is dependent on what the internal resistance of the LDR is.
For the LDR that we supply with the Bolt kit the required resistance is 10kOhm.
Pull ups are commonly 10k on-board and lower values like 2k2 off-board.
The higher the value less power is wasted, but the noise pickup susceptibility is greater, any value from 100 ohms to 10M can work, but the rule of thumb is 10k is adequate to protect against noise on-board. So we use 10k ohm resistor in our bolt circuit.
We use 10k ohm resistor because the the resistance offered by it is inversely proportion to the light intensity i.e if light falling on it is more then the resistance decreases and hence the voltage drawn also decreases. And if resistance value is high then voltage drawn is also large.
That is why we are provided with 10k ohm resistor in the Bolt iot kit