Self Test on Tutorial 10



For the mains, the potential difference changes direction with a frequency of …………. Hz


This means that one complete cycle takes time T =



The potential difference is given as ……….. V. In fact the peak p.d., V0­, is more like 325V


Label the two axes with the quantities that can be measured with the CRO




The average p.d would be …………. but this is not very useful – energy is obviously being transferred so, to get some idea of an ‘average’, it is useful to look at the power delivered.


Heating effect


Power  P = IV =


For the peak current, I0 =


If I = 0, power =


The mean power =


Show these quantities on the axes






The root mean square value of I for a.c. Irms, is the current (dc) that would give the same power as the mean (ac) power


        Irms 2  =


         Irms   =


Also   Vrms =                              eg for the mains, V0  = 325 V  so Vrms =