Question

In Oersted's experiment, suppose that the compass was 0.16 m from the current-carrying wire. If a magnetic field of one third the Earth's magnetic field of 5.0×10?5T was required to give a noticeable deflection of the compass needle, what current must the wire have carried?

Answer 1

Magnetic field due to a current carrying wire at a perpendicular distance 'd' is given by,

B = *I/(2*pi*d)

here, I = current in wire = ??

d = perpendicular distance = 0.16 m

Be = Earth's magnetic field = 5.0*10^-5 T

B = (1/3)*Be = (1/3)*5.0*10^-5 T, (To give a noticeable deflection of the compass needle.)

then, I = 2*pi*d*Be/(3*)

I = 2*pi*0.16*(5.0*10^-5)/(3*4*pi*10^-7)

I = 13.33 Amp = current in wire

Let me know if you've any query.