# Physics

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In Oersted's experiment, suppose that the compass was 0.30 m from the current-carrying wire. If a magnetic field of 1/3 the Earth's magnetic field of 5 10−5 T was required to give a noticeable deflection of the compass needle, what current must the wire have carried? I really need some help on this.

• Physics -

Magnetic field of the current-carring wire at distance b from it is
B=1/2πb
If B=B(Earth)/3= 5•10⁻⁵/3 T,
I=2πbB= 2π•0.3•5•10⁻⁵/3 = …

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