- #1
rainstom07
- 16
- 0
My professor asked the cost of running a hair dryer of 1500 W for 15.0 minutes for 5 days a week for 4 weeks. The utility company charged $0.60 per kWh.
Instinctively, i thought to combine 1500 W with the 15.0 minutes into my version of "kilowatt per hour".
[tex]1500 W * \frac{1 KW}{1000 W} = 1.50 kW[/tex]
[tex]1.50 min * \frac{1 hr}{60 minutes} = 0.25 hr[/tex]
thus:
[tex]\frac{1.50 kW}{0.25 hr} = 6 kW/hr[/tex]
The dryer was used 5 times a week for 4 weeks... so it was used 20 times in the 4 weeks.
[tex]6 kW/hr * 20 = 120 kW/hr[/tex]
At... $0.60 per kWh
[tex]120 kWh * 0.60 \frac{$}{kWh} = $72[/tex]
The answer was $4.5 not $72. Therefore, my concept of kWh is clearly wrong.
Can someone explain to me what kWh is intuitively? It clearly is not the amount of kW consumed in an hour.
Thanks in advance!
Instinctively, i thought to combine 1500 W with the 15.0 minutes into my version of "kilowatt per hour".
[tex]1500 W * \frac{1 KW}{1000 W} = 1.50 kW[/tex]
[tex]1.50 min * \frac{1 hr}{60 minutes} = 0.25 hr[/tex]
thus:
[tex]\frac{1.50 kW}{0.25 hr} = 6 kW/hr[/tex]
The dryer was used 5 times a week for 4 weeks... so it was used 20 times in the 4 weeks.
[tex]6 kW/hr * 20 = 120 kW/hr[/tex]
At... $0.60 per kWh
[tex]120 kWh * 0.60 \frac{$}{kWh} = $72[/tex]
The answer was $4.5 not $72. Therefore, my concept of kWh is clearly wrong.
Can someone explain to me what kWh is intuitively? It clearly is not the amount of kW consumed in an hour.
Thanks in advance!