formulas please

[searley]

could some one show me how to get the formulas and working out with these.

1,a capacitor of 95uf is connected in parallel with a 20ohm pure resistor the group is connected to a 230v 50hz supply. calculate the power = 2.64

2,a small heating circuit draws 1.5kw of power and has an internal resistance of 0.5ohm. what is the total current draw = 55A

3a 90mf capacitor is connected to a 100volt d.c supply.calc the charge stored in the capacitor = 9 coulombs

 

[msb2003]

1. As the capacitor is connected in parallel, treat it on its own. A pure capacitor giving a 90 degree leading current, p.f. 0 takes no power. Therefore you can work the calculation as a purely resistive circuit

I = V/R =230/20 =11.5

P= IV = 11.5 x 230 = 2.645KW

2. P=Isquared R I = square root (PR) = SR(1500 / 0.5) = 54.77A

3. Q = CV = 0.09 x 100 = 9 coulombs

I hope that helps