Question

You are out of gas in the desert and you accidently dropped your phone battery down an Abandoned oil well. You have a charged car battery (12 volts) and a bunch of resistors and wire. You want to power your cell phone with this battery but the cell phone only operates if it has 3.6 Volts across its power terminals. (3.7 Volts will destroy the phone and 3.5 will fail to operate the phone.) If the cell phone uses 0.15 Amperes in all modes, design a circuit that will operate your cell phone from this car battery and let you call for help.

Answer 1

See the attachment

Step-by-step explanation:

Connecting a resistor in series with battery will cause the battery voltage to drop.

voltage across resistor= 12-3.6= 8.4

Current in the circuit= 0.15A

V= IR

8.4= 0.15R

R= 56Ω

From the bunch of resistors, I will make a combination of 56Ω