A 12V dc source is to be divided so that 9V appears across the lower resistor of a two-resistor series arrangement while the current drawn from the source does not exceed 20mA.
(i) Determine the total resistance that must be present in the series circuit to satisfy the given current limit.
(ii) Find the ratio of the lower resistor to the total resistance required to obtain 9V across it.
(iii) Choose suitable integer values of R1 (upper resistor) and R2 (lower resistor) that simultaneously meet both conditions, and verify that the design objectives are achieved.