A class has a 400-turn air-core solenoid, adjustable low-voltage supply, ammeter, Hall probe and temperature sensor. (a) Formulate a question about current and central magnetic flux density. [2] (b) Give and justify a hypothesis. [3] (c) Design a method from 0.10 A to 1.00 A, including variables, repeats, zero correction, graph choice and safety. [7] (d) Explain how to modify the method to test the effect of turns per metre. [2] Do not invent results.

Question

Accepted Answer

Vary current and measure axial field at the fixed centre while controlling coil geometry, probe orientation, temperature and nearby magnetic materials. Predict a proportional field–current relationship within the supply and heating limits. (a) Ask: How does current from 0.10 A to 1.00 A affect magnetic flux density at the geometric centre of this fixed air-core solenoid? (b) Predict B proportional to I because each turn's field contribution increases with current and superposition adds the contributions. This model assumes unchanged geometry and negligible magnetic material effects. (c) Clamp the solenoid, align and mark the Hall probe at its centre, measure ambient field with zero current, then take readings at ten planned current settings in random order after the value stabilises. (c) Control turns, coil length, probe position and orientation, distance from magnetic objects and coil temperature. Subtract the signed zero-current reading; repeat complete current sequences rather than only repeated display readings. (c) Plot corrected B against measured I with repeat spread. Use a current limit and series protection, switch off between readings, monitor temperature, avoid short circuits and do not touch a hot coil. (d) To test turns per metre, prepare equal-length coils with different known turns, use the same current and centre-probe geometry, and keep wire heating comparable. Plot B against N/L.

Design a solenoid field investigation

What a complete response should do

How did this one feel?