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Activate 12V Relay with a 5V GPIO

What is the reason of using 10K resistor in series to the control? is it related to the base current according to the NPN transistor's datasheet?

For example: my CONTROL/GPIO is 5V the maximum base current according to the NPN transistor's datasheet is 120mA Does it means I need to have minimum 42R resistor?

Thanks, Roy

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