Find the magnetic field at the center

[Fatima Hasan]

Homework Statement

A wire carrying current I=7A is shaped as half circle of radius R=0.2m.The magnetic field B(in μT) at the center is :
A)11.0(k)
B)7.9(k)
C)9.4(k)
D)6.3(k)
E)4.0(-k)

Homework Equations

B=(μ₀ I)/(2πR)

The Attempt at a Solution

B = (4π*10^-7 *7)/(0.2*2*π) * 0.5 (Multiply by 1/2 because the wire is shaped as half circle).
B = 3.5*10^-6 T = 3.5μT
Could anyone tell me where is my mistake?

 

[Gene Naden]

The formua for B that you used is for a straight wire. This wire is not straight.

 

[Fatima Hasan]

The formua for B that you used is for a straight wire. This wire is not straight.

B = (μ*I)/(4*π*r) *θ ?

 

[Gene Naden]

What is $\theta$ in your formula?

 

[Fatima Hasan]

What is $\theta$ in your formula?

B = (μ*I)/(2R) *0.5
= ( 4*10^-7π *7)/(2*0.2) *0.5
= 10.99μT
=11 μT