# Fields QuestionWatch

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#1
If the earth has a charge of 1.0 × 10^6 C, find the B-field at the sun due to the motion of the
earth, given that the earth’s velocity relative to the sun is 30 kms−1 and the radius of the
earth’s orbit is 1.5 × 10^11 m

edit: so i have tried using E = kq/r^2= (8.99x10^9)(1x10^6)/(1.5x10^11)^2
that gives 3.995.....x10^-7

Then i use V = E /B ==> B = E / V

B = 3.995 x 10^-7 / 30000

i get B = 1.33 x 10^-11

but the answer is 1.3 x 10^-19

where have i gone wrong

Thanks
Last edited by fyaa79; 1 month ago
0
1 month ago
#2
I don't think you should just use random equations!
You could work out the 'current' as charge / time for earth to orbit
then use the equation for B in the centre of a coil.
Post your working if that doesn't work for you.
0
#3
how would i use I = Q/t , i have not been given time
(Original post by old_teach)
I don't think you should just use random equations!
You could work out the 'current' as charge / time for earth to orbit
then use the equation for B in the centre of a coil.
Post your working if that doesn't work for you.
0
1 month ago
#4
You have the speed and distance (circumference of orbit)
0
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