Suppose that an electromechanical relay has a coil voltage rating of 5 volts, and a coil resistance of 55 Ω. However, you desire to energize this relay with a 9 volt batt. You know that a series-connected resistor might enable the 5-volt relay coil to be powered by the 9-volt supply without damage, but you do not know what size of resistor would be appropriate for the task.
Explain how the resistor's value would be calculated, along with the calculated value in ohms.
Thanks.