**Problem 2.1** A laptop computer is powered by a power supply that
delivers 4.5 A at 16 V. The efficiency of the power supply is 85%.

**(a)** If the computer is turned on at all times, how many kilowatt-hours does the
power supply use in 24 hours?

**(b)** If the price per kWh is 12 cents, how much does it cost to run the computer
continuously for one week?

**Problem 2.2** Consider the following circuit.

**(a)** Compute the power absorbed by each of the resistors. Hint:
Compute the equivalent resistance for the combination of the 150 and
820 ohm resistors first. Then you can compute the total current
delivered by the power supply and the voltage across the 150 and 820
ohm resistors.

**(b)** If you only have 0.25 W resistors with standard values
(100, 120,150, 180, 220, 270, 330, 390, 470, 560, 680, 820, 1.0k,
1.2k, 1.5k, 1.8k, 2.2k, 2.7k, 3.3k, 3.9k, 4.7k, 5.6k, 6.8k, 8.2k, 10k)
available, how would you modify the circuit so that no resistor burns up
and the resistances in the given circuit remain within 5% of their
labeled values?

©2008, 2013-2014, P. Mathys. Last revised: 01-21-14, PM.