A clock face has negative charges –q, –2q, –3q, ... -12q fixed at the position of the corresponding numerals on the dial. The clock hands do not disturb the net field due to the point charges. At what time does the hour hand point in the direction of the electric field at the centre of the dial?

Let E be the field at the centre of the dial due to a charge ‘q’
The resultant field due to the charges at the numerical
a) 1 and 7  is  6E  towards  7
b) 2 and 8 is  6E  towards  8
c) 3 and 9  is  6E  towards  9 
d) 4 and 10  is  6E  towards 10
e) 5 and 11  is  6E  towards 11 
f) 6 and 12  is  6E  towards 12
Now the resultant field due to (g) 6E at 12 and 6E at 8 is 6E and it is along (10) and (h)  6E 11 and 6E at 7 is 6E and it is along (9)
Finally the are t intensity due to 12Eat 9 and 12E at 10 is in between 9 and 10.
Hence the time in the clock is 9:30hr.