You are Here: Home >< Physics

# Electric Field in Equilateral Triangle

Announcements Posted on
Would YOU be put off a uni with a high crime rate? First 50 to have their say get a £5 Amazon voucher! 27-10-2016
1. An equilateral triangle is made of 3 rods, each 0.1m in length. Rods AB and BC are charged +18nC and rod AC is charged -18nC. What is the electric field at the center of the triangle?

Here is my solution, but it is apparently incorrect:

Since all of the rods have the same magnitude of charge, they all generate the same magnitude of field.

r=1/2h where h=height of the triangle.
h=sqrt(L^2-(.5L)^2)=sqrt[(.2^2m)-(.1^2)]=0.173m
h/2=0.0866m

E=kq/r^2=(8.99x10^9)(18x10^-9)/(0.0866^2)
E=2.158x10^4N/C

In the triangle, EABx=-EBCx and EACx=0, so we only need to focus on the y direction.

Since this is an equilateral triangle, all of the angles are 60 degrees

My thought would be that Enet=EABY+EBCY+EAC
so Enet=2Esin(60)+E=2(2.158x10^4sin (60))+2.158x10^4
Enet=5.89x104N/C
This is the answer I got, but apparently it is incorrect. Any idea where I went wrong?
2. (Original post by PatchworkTeapot)
An equilateral triangle is made of 3 rods, each 0.1m in length. Rods AB and BC are charged +18nC and rod AC is charged -18nC. What is the electric field at the center of the triangle?

Here is my solution, but it is apparently incorrect:

Since all of the rods have the same magnitude of charge, they all generate the same magnitude of field.

r=1/2h where h=height of the triangle.
h=sqrt(L^2-(.5L)^2)=sqrt[(.2^2m)-(.1^2)]=0.173m
h/2=0.0866m

E=kq/r^2=(8.99x10^9)(18x10^-9)/(0.0866^2)
E=2.158x10^4N/C

In the triangle, EABx=-EBCx and EACx=0, so we only need to focus on the y direction.

Since this is an equilateral triangle, all of the angles are 60 degrees

My thought would be that Enet=EABY+EBCY+EAC
so Enet=2Esin(60)+E=2(2.158x10^4sin (60))+2.158x10^4
Enet=5.89x104N/C
This is the answer I got, but apparently it is incorrect. Any idea where I went wrong?
Have you been told to use E=kq/r^2? That's not the electric field from a rod...

## Register

Thanks for posting! You just need to create an account in order to submit the post
1. this can't be left blank
2. this can't be left blank
3. this can't be left blank

6 characters or longer with both numbers and letters is safer

4. this can't be left empty
1. Oops, you need to agree to our Ts&Cs to register

Updated: September 18, 2016
TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Today on TSR

Find out here

### How to cope with a heavy workload

Poll
Study resources

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.