Solving Magnetic Fields: Find Electric Field Zero Point

In summary, the problem involves calculating the point at which the magnitude of the electric field is zero between two small charges of 6e-5 and -2e-5 C placed 0.36m apart. Using the equation EF = (k q) / r^2, where k = 9e9 and EF = 0, and setting the distance from one charge to the point of zero electric field as x, the distance from the other charge would be (0.36 + r). By equating the electric fields at point P due to the positive and negative charges, the value of r can be solved for. The correct answer is 0.49m.
  • #1
Matt1234
142
0

Homework Statement



Two small charges 6e-5 and -2e-5 C. are placed 0.36m apart. Calculate the following:
e) the point at which the magnitude of the electric field is zero.



Homework Equations



EF (field) = (k q) / r^2

where EF = 0

k = 9e9

The Attempt at a Solution



I know I am looking for r, but the way i setup the equation gives me 2 unknowns.
 
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  • #2
Distance between the two charges is 0.36cm, so put the point where E=0 as a distance x from one charge, so the distance from the other charge would be?
When you get that, you will have the equation with one unknown.
 
  • #3
im sorry i don't understand. if i set one r to 0.36 and solve for the other?

i tried that and i get 0.2 which is wrong. I am not 100% sure about this part "put the point where E=0 as a distance x from one charge"
 
  • #4
Matt1234 said:
i tried that and i get 0.2 which is wrong. I am not 100% sure about this part "put the point where E=0 as a distance x from one charge"


+ _______________ -
(0.36cm)


+ ______ (E=0) _______ -
(x) (p) ??


if the distance from + to - is 0.36cm (top diagram), then what the '??' equal to in the second diagram? (something-x, what is that something?)

When you get that, can you find the electric field at point P (where E=0) due to the +ve charge in terms of x? Similarly, do the same for the electric field at point P due tot he -ve charge. Those two are equal, you can now find x.

EDIT: my diagrams are not coming out correctly. So for the second one, under the first line is 'x', under the E=0 is 'P' and under the second line is '??'
 
  • #5
(0.36 - r) i believe is what I am looking for?

Making this question quadratic?

i got the root to be 0.56 which.

The answer is 0.49m

under the first i used:

(0.36^2) under the second i used ( x -0.36)^2 which made it quadratic.
 
Last edited:
  • #6
Matt1234 said:
(0.36 - r) i believe is what I am looking for?

Making this question quadratic?

Yes.
 
  • #7
ok I am quite confused as i keep getting 0.56 yet the answer is 0.49 m

ill show the teacher my work tom. thank you.
 
Last edited:
  • #8
Matt1234 said:
ok I am quite confused as i keep getting 0.56 yet the answer is 0.49 m

ill show the teacher my work tom. thank you.

Oh wait, I am sorry, I read the question with the two charges being positive (andyet drew the diagram with + and - :confused:)

BUT the second diagram should be this.


+ ________(0.36m)_________ - ____(r m)_____(P)

SO what you need to do is find the E field at point P due to the -ve charge. Then find the E field due to the +ve charge, and then equate those two.
The distance of the +ve charge to P is (0.36+r) NOT (0.36-r) which would mean that E=0 between the two charges.

All you need to do to rectify the problem is change the sign in your first equation in your working and you should get the correct answer. Sorry again for confusing you there.
 

1. How do you determine the zero point of an electric field in a magnetic field?

To find the zero point of an electric field in a magnetic field, you can use a magnetometer or a compass to measure the direction and strength of the magnetic field. Then, you can use the right hand rule to determine the direction of the electric field and find the point where it crosses the zero line.

2. What is the significance of finding the zero point of an electric field in a magnetic field?

The zero point of an electric field in a magnetic field is important because it tells us where the electric field is equal to zero, indicating a balance between the magnetic and electric forces. This can help us understand the behavior of charged particles in a magnetic field and can also be used in various applications, such as in the design of magnetic shields.

3. Can the zero point of an electric field in a magnetic field be manipulated?

Yes, the zero point of an electric field in a magnetic field can be manipulated by changing the strength or direction of the magnetic field. This can be done using electromagnets or by moving the source of the magnetic field.

4. Are there any real-life applications of finding the zero point of an electric field in a magnetic field?

Yes, there are many real-life applications of finding the zero point of an electric field in a magnetic field. Some examples include the use of magnetic shielding in electronic devices, the development of particle accelerators, and the study of Earth's magnetic field to understand its effects on our planet.

5. Are there any other methods for solving magnetic fields besides finding the electric field zero point?

Yes, there are other methods for solving magnetic fields, such as using mathematical equations and numerical simulations. These methods can be used to analyze more complex magnetic fields, including those with changing strengths and directions. However, finding the electric field zero point is a simple and effective method for understanding the basic behavior of magnetic fields.

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