Question

Hii..

can anyone solve this please?
no spams

Answer 1

Hey there :

We know that solenoid is the soft iron core wound by the coil...

And magnetic field due to solenoid is given by

=> B =uni

Where u = 4π ×10^-7 T/amp m

=> n = turn density or lenght per unit distance
=> i is current

Now put the value as given..

Here given :
B = 20 mT = 20 × 10 -³ T
n = 20 turns per cm = 20 turns / 10-²m = 20 ×10² turns per m

Now using / B = uni

= > i = B/un =( 20 × 10 -³) /{4π×10-7 × 20 ×10²}

=> i = 100/4π = 25×7/22 { put π = 22/7}

=> i = 7.95 A

And in above question " asking for near value and its nearly equal to 8.0 A

So, I = 8.0 A....