Electric Field question - Why is this answer negative

AI Thread Summary
The discussion addresses confusion over why electric field answers are negative in a given problem. It clarifies that electric fields originate from positive charges and terminate at negative charges, with the field direction being crucial for calculations. At a point between a positive and a negative charge, the electric fields from both charges point in the same direction, contributing to a negative value on the horizontal axis. This understanding resolves the initial confusion about the sign of the answers. The explanation effectively clarifies the concept of electric field direction and its implications for the problem at hand.
cros0
Messages
4
Reaction score
1
upload_2016-5-20_18-3-37.png

upload_2016-5-20_18-3-50.png


Hello. The first image is the question, the second image is from the solutions manual. I don't understand why these answers are negative. Anyone have a clue?
 
Physics news on Phys.org
cros0 said:
View attachment 101011
View attachment 101012

Hello. The first image is the question, the second image is from the solutions manual. I don't understand why these answers are negative. Anyone have a clue?
Sure. (and Welcome to the PF)

Electric field points from positive charges to negative charges. So the E-field at the first negative charge is pointing inward to that negative charge in all directions. The E-field at the positive charge is pointing away from it in all directions. They ask for the sum of the two E-fields at a point between them, so both components point to the left, which is the negative direction on the horizontal axis.

Does that help? :smile:
 
Seems reasonable enough, and I feel much better now. Thanks!
 
  • Like
Likes berkeman
Thread 'Voltmeter readings for this circuit with switches'
TL;DR Summary: I would like to know the voltmeter readings on the two resistors separately in the picture in the following cases , When one of the keys is closed When both of them are opened (Knowing that the battery has negligible internal resistance) My thoughts for the first case , one of them must be 12 volt while the other is 0 The second case we'll I think both voltmeter readings should be 12 volt since they are both parallel to the battery and they involve the key within what the...
Thread 'Struggling to make relation between elastic force and height'
Hello guys this is what I tried so far. I used the UTS to calculate the force it needs when the rope tears. My idea was to make a relationship/ function that would give me the force depending on height. Yeah i couldnt find a way to solve it. I also thought about how I could use hooks law (how it was given to me in my script) with the thought of instead of having two part of a rope id have one singular rope from the middle to the top where I could find the difference in height. But the...
Back
Top