Question

13 and 17 ..just do that

Answer 1

Question 13. Define watt-hour. How many joules are in 1 watt-hour?

Answer. A watt-hour  is a unit of Electrical Energy which can be numerically written as Power × time. 1 watt hour means that,

→ 1 Wh = 1 J/s × 60 × 60 s

→ 1 Wh = 3600 J or 3.6 × 10³ Joules

______________________________

Question 17. An elecyric kettle rated at 220 V, 2.2 kW and works for 3 hr. Find energy consumed and the current lost.

Solution : Power = Vi

→ 2.2 kW = 220 V × i

→ 2200 W = 220 V × i

→ 10 A = i

Hence 10 Ampere of electric current is drawn.

→ Electric Energy = Vit

→ E = 220 V × 10 A × 3 hr

→ E = 220 V × 10 A × 3 × 60 × 60s

→ E = 23760000 J or 23760 kJ

Or simply, 2.2 kW = Energy/3hr

→ 6.6 kWh = Energy

Hence electric energy of 23760 kJ or 6.6 kWh is produced.