Please show why these are correct answers.

14. Two charges +Q, and -Q are located a distance r away from the origin. The first charge is on the x-axis and the second charge is on the y-axis, as shown. What is the magnitude of the electric field at the origin? A. KQ 7 2 B. 2kQ 7 2 V2 KQ C. +Q D. KQ 472 E. Zero 15. Suppose I am attempting to determine the electric field at a particular location in my lab. I observe that an object carrying +3C of electric charge experiences a 15N force at that point. What is the magnitude of the electric field at this location? A. 0.2 N/C B. 1.5 N/C C. 3 N/C D. 5N/C E. 12 N/C 16. Consider the same scenario described in the previous problem. If a colleague of mine tries to determine the electric field at the same location using a -6C charge, what should I expect about his calculation of the electric field? A. His value of the electric field will be two times larger than mine B. His value of the electric field will be two times smaller than mine C: His value of the electric field will be exactly the same as mine D. His result will be invalid, because you cannot determine electric field with a negative test charge 17. An atom (maybe ionized, maybe not!) is at rest in a region of low potential. I move the particle to a region of higher potential and bring it to rest there (no gravitational forces were at work). If I did exactly zero work during this process, what can you conclude about the atom's properties? A. It is electrically neutral B. It is positively charged C. It is negatively charged D. None of these things can be determined for certain