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2009-12-08T15:38:01+01:00
W=Pc*t
Pc=W/t=18000000J/36000s=500W
η=Pu*100%/Pc
Pu=η*Pc/100=80*500/100=400W
2.
I=U/R=200V/500=0,4A
W=U*I*t=200V*0,4A*300s=24000Ws=24kWs=24kJ
1 5 1
2009-12-08T17:24:02+01:00
1.
W = 18 MJ = 18 000 000 J
t = 10h = 10*3600s = 36 000 s
η = 80%

P = W / t
P = 18000000J/36000s = 500W

η = Pu * 100% / P
Pu = η * P / 100
Pu = 80*500/100 = 400W

2.
R = 500Ω
U = 200V
t = 5min = 5 *60s = 300s

I = U / R
I = 200V / 500Ω = 0,4 A

W = U * I * t
W = 200V * 0,4A * 300s = 24000 Ws = 24000J = 24kJ