Our recent lab was \"Measurement of the Magnetic Field of the Earth\". During th

Question

Our recent lab was "Measurement of the Magnetic Field of the Earth". During this lab, we placed a compass in the center of a wire coil connected to an ammeter and a power source (via a switch). We then rotated the coil so that the local field was in the plane of the coil and increased the current in the coil until the compass needle pointed at 45 degrees to the plane of the coil. We then reversed the switch and again increased the current until the compass needle pointed at 45 degrees to the plane of the coil. The question I'm stuck on has two parts: What would be the effect on the required current if the coil had twice its diameter? Likewise, what if it had twice the number of turns on the coil? (for the record, our coil had 5 turns).

Explanation / Answer

If diameter of coil is twice than area of coil is increases 4 times ...And resistance of coil decreases up to 4 times ..

Because resistance is inversely proportional to area.

If resistance decreases 4 times than current in the coil is increases 4 times...By ohm's law...

2. Current in the coil doesn't depend on number of turns...So current remains same

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