A few prelim physics questions (1 Viewer)

[TheStallion]

Hey guys,

I've worked out the questions that are listed below, but i'm not that certain that I did them correctly. If you guys could help me out with calculating them with working, it'd be great.

Q20) An electric heater, operated from the 240V A.C main supply is rated at 2.4kW. Calculate:

a) the current drawn by the electric heater during use at the rated power.
b) the heat energy produced by the electric heater in a time period of 5 hours, assuming 100% efficiency.
c) the cost of running the electric heater for the 5 hours at $0.15 per kilowatt-hour.

Thanks everyone!

 

[kaz1]

Vaguely remember how to do a)

P=VI
2400=240xI
I=10A

 

[TheStallion]

Ok that's great, means that I did that one right - now hopefully people know b and c.

 

[darkchild69]

Hey guys,

I've worked out the questions that are listed below, but i'm not that certain that I did them correctly. If you guys could help me out with calculating them with working, it'd be great.

Q20) An electric heater, operated from the 240V A.C main supply is rated at 2.4kW. Calculate:

a) the current drawn by the electric heater during use at the rated power.
b) the heat energy produced by the electric heater in a time period of 5 hours, assuming 100% efficiency.
c) the cost of running the electric heater for the 5 hours at $0.15 per kilowatt-hour.

Thanks everyone!

a) P = IV
2400W = 240I
I = 2400/240
I = 10A

b) E = Pt
E = 2400*5*60*60
E = 43,200,000J
E = 43.2MJ

c) 2.4kW @ 5 hours = 12kWh

Cost = 12 * 0.15
Cost = $1.80

(Alternatively, [43,200,000J/(1000*3600)] = 12kWh)

 

[TheStallion]

Thank god, I got them right. Thanks a lot darkchild69 and kaz1. Rep +.