2 Problems involving electric field and work

[nutella]

Homework Statement

Excuse my excellent paint skills
http://imgur.com/PbXdlOW
If the work done by a charge from z to y is W. Would the work be different if it was from z to x then to y.

Homework Equations

W=vQ

The Attempt at a Solution

I said it would be the same because delta v would be the same in the end

1. The problem state, all variables and give/known data
http://imgur.com/RkG05ph
What is the electric field at the point z and what is the direction

Homework Equations

E=kq/r^2

The Attempt at a Solution

I assume the positive and negative would cancel each other out. The distance between the charge and the center is d rad(2)/2 so the charge for one of them would be KQ/(2d^2/4)= 2KQ/d^2 then you just multiply that by 2 because there is two charges, but i don't know the direction

 

[DrClaude]

The fact that you don't know the direction in the last problem is an indication that you did something wrong. Can you justify

I assume the positive and negative would cancel each other out.

 

[nutella]

My teacher showed us a problem where the opposite corners were opposite charges and he said the electric field at the middle is zero.

 

[DrClaude]

What happens if you put a test charge in the middle?