At the end of a 31 day period, your utility bill shows that you have used 1500 kWh. What is your average daily power usage?
An electric heater works on 120 V and draws 3 A of current. How much power does it use?
A 56 resistor is connected across the terminals of a 1.5 V battery. What is the power dissipation in the resistor?
The maximum voltage is 1 V and the maximum current is 1 A in a given resistor. Should a 1 W or a 2 W resistor be used? Why?
A 50 load uses 1 W of power. What is the output voltage of the power supply?
How much average current can be drawn from an 80 Ah battery for 10 h?
A certain power supply provides a continuous 2 W to a load. It is operating at 60% efficiency. In a 24 h period, how many kilowatt-hours does the power supply use?

8.21 Consider the plate dealt with in Example 8.1. Ploth as a function of the angle of inclination of the plate as the hot side is tilted both upward and downward over the range +90. Note that you must make do with discontinuous formul in different ranges of 0. Example 8.1 Verify the first heat transfer coefficient in Table 1.1. It is for air at 20C next to a 0.30 m high wall at 50C. SOLUTION. At Tf = 35C = 308 K, we find Pr = 0.710, v = 1.643 x 105 m/s, a = 2.315 x 10-5 m/s, and k = 0.02672 W/m-K. At T = 20C, B = 1/(273+20) = 0.00341 K-. Then 9.8(0.00341) (30) (0.30) (1.643) (2.315)10-10 7.12 x 10 The Churchill-Chu laminar correlation, eqn. (8.13a), gives (7.12 x 107)/4 [1+ (0.492/0.710) 9/16]4/9 so gBATL av RaL = NuL = 0.68 +0.67- 0.02672 0.30 h = 47.91 This value matches Table 1.1. = 4.26 W/mK = 47.91