p. 45 Solutions

1. P = VI = 110(7) = 770W = 0.770 kW

E = Pt = 0.770 kW(12 h) = 9.24 kWh

C = Er = 9.24 kWh($0.05/kWh) = $0.46

2. P = VI = 120(15) = 1800 W = 1.8 kW

E = Pt = 1.8 kW(200 h) = 360kWh

C = Er = 360 kWh($0.053/kWh) = $19.08

3. P = 0.2 kW

E = Pt = 0.2 kW(5 h) = 1 kWh

C = Er = 1 kWh($0.05/kWh) = $0.05

4. P = 4.5 kW

E = Pt = 4.5 kW(30*2 h) = 270 kWh

C = Er = 270 kWh($0.052/kWh) = $14.04

5. P = 4.5 kW

E = Pt = 4.5 kW(2 h) = 9 kWh

C = Er = 9kWh($0.0454/kWh) = $0.41

6. P = 1.2 kW

E = Pt = 1.2 kW(60d * 90/60 h/d) = 108kWh

C = Er = 108 kWh($0.046/kWh) = $4.97

7. P = 0.145 kW

E = Pt = 0.145 kW(30d * 8 h/d) = 34.8 kWh

C = Er = 34.8 kWh($0.05/kWh) = $1.74

8. P = 1.5 kW

E = Pt = 1.5 kW(330 h) = 495 kWh

C = Er = 495 kWh($0.05/kWh) = $24.75

9. B

10. B

11. 2 and 4