Electric Power and Cost

1 (a)      P = VI               P power in W

                                    V p.d. in V       

                                    I current in A

3000 = 240 x I

I=3000/240 =12.5A

(b)      V = IR

240=12.5R

R = 240/12.5 = 19.2 Ω

(c)      3 kW = 3000 W = 3000 joules per second

Energy used in 1 min = 3000 x 60 = 180 000 J

2        8A       31.25Ω

3        Resistance depends upon temperature

4        1 641 600 J

5        4800J

6        6

7        2.083 kW

8        1920W 1687.5 W

9        .64m

10.     21.6p  19.1p

11      £1.16

12      0.54kWh

13      .42 kWh        .112p + 3.79p = 3.9p

14      4.46p            9.34p

Extra  50kW  0.072W