1.
[tex]Dane:\\t = 2 \ h =2\cdot3600 \ s = 7200 \ s\\U = 230 \ V\\I = 8 \ A\\Szukane:\\W = ?\\P = ?\\\\Rozwiazanie\\\\W = U\cdot I\cdot t\\\\W = 230 \ V\cdot 8 \ A\cdot7200 \ s\\\\\boxed{W = 13 \ 248 \ 000 \ J = 13 \ 248 \ kJ = 13,248 \ MJ}\\\\1 \ kJ = 1000 \ J\\1 \ MJ = 1 \ 000 \ 000 \ J\\\\\\P = U\cdot I\\\\P = 230 \ V\cdot8 \ A\\\\\boxed{P = 1 \ 840 \ W = 1,84 \ kW}[/tex]
2.
[tex]Dane:\\P = 20 \ W\\I = 0,8 \ A\\Szukane:\\U = ?\\\\Rozwiazanie\\\\P = U\cdot I \ \ /:I\\\\U = \frac{P}{I}\\\\U = \frac{20 \ W}{0,8 \ A}\\\\\boxed{U = 25 \ V}[/tex]
3.
[tex]Dane:\\P = 40 \ W=0,04 \ kW\\t = 5 \ h\cdot30 = 150 \ h\\k = 0.80\frac{zl}{kWh}\\Szukane:\\K = ?\\\\Rozwiazanie\\\\W = P\cdot t\\\\W = 0,04 \ kW\cdot150 \ h = 6 \ kWh\\\\K = k\cdot W\\\\K = 0,80\frac{zl}{kWh}\cdot6 \ kWh\\\\\boxed{K = 4,80 \ zl}[/tex]
