Wires 12 Suppose we can model a cell phone connected to a charger with the circu

Question

Wires 12 Suppose we can model a cell phone connected to a charger with the circuit shown. The charger is a voltage source, the wires between the charger and phone have some resistance (12 ), and the cell phone Cell Phone modeled as two resistors (45 and 10 ). Use this Charger is 45 : circuit for the following problems. : 10 29. How much current (I) flows into the cell phone? A. 0.075 A B. 0.091 A C. 0.42 A D. 1.10 A . What is the voltage drop across the wires (resistance at top)? A. 0.75 V B. 0.90 V C. 3.36 V D. 5 V How much power is delivered to the cell phone (both resistors together)? A. 67 mw B. 251 mW C. 306 mW D. 373 mW

Explanation / Answer

a ) The total resistance in the circuit is 45 + 10 + 12 = 67 ohms and the voltage is 5 V . Since this is a series circuit the same current flows across the cicuit given by

current = voltage
------------- = 5 / 67 = 0.0746 = 0.075
Resistance

b ) voltage drop across 12 ohms = 12 * 0.075 = 0.90 volts

c ) Resistance of cell phone is 45 + 10 = 55

power is current ^2* resistance = 0.075^2 * 55 = 306 mW

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