hi, i have attached the picture to my question... can someone please help me solve this..

Question

anonymous · Answer

attachment

farcher · Answer

1 E-field is away from a positive charge and towards a negative charge.
2 E-field from a point charge is radial - ie like the spokes of wheel
3 The distance to P from the two charges is the same.
4 The strength of the E-field is proportional to the charge.
5 Draw a line starting at the +4 charge which passes through P and beyond.  
6 Draw a vector (line length 2 cm + arrow) to represent the E-field from the + 4 charge.  
7 Repeat for the -8 charge noting that the vector will be of a different but known length.
8 Complete the parallelogram and show the appropriate diagonal as the vector R.

I can show you the answer when you have done it but do ask again if you get stuck.

anonymous · Answer

thanks for your help... i finally understood :)

farcher · Answer

The diagram is attached.

anonymous · Answer

how do you know the lengths of the horizontal and vertical vectors?

farcher · Answer

Because the magnitudes of the charges are 4 and 8 all you need to draw is two vectors one (for the -8 charge) which is twice the length of the other.