Describe a solenoid field investigation
Use filings and compass readings inside and outside a fixed solenoid, retaining supply and heating controls.
Core and Extended; Physics 0625, 2026–2028. Use the stated source, operating conditions and meter ranges. Written practice is self-checked.
Before you begin
- Describe the solenoid field and poles.
- Distinguish a current change from a material change.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
What should be recorded when inserting an iron core during a comparison?
What you will learn
- Use filings and compass readings inside and outside a fixed solenoid, retaining supply and heating controls.
- Plan separate pattern and direction observations with coil, core and background conditions controlled.
Map both interior and exterior
Place a suitably arranged school solenoid around or alongside a card so that both its axis region and outside can be investigated. Connect it to a teacher-supervised low-voltage, current-limited circuit. Keep coil position and supply settings fixed while lightly distributed filings reveal the broad bar-magnet-like pattern.
Use a small compass at accessible marked points along the axis and outside each end. Record north-tip directions after settling, identify the north and south ends, and add arrows for internal S-to-N and external N-to-S continuation. Filings alignment alone does not assign these senses.
State observations and fair controls
Compare current off and on to identify background contributions. Keep nearby magnetic material, lead geometry and coil orientation unchanged. Use apparatus that allows readings without forcing a large compass into a small coil or disturbing the turns. A broad pattern is evidence, not an exact numerical strength measurement.
Avoid overheating with teacher-chosen current limits and observation times; do not power a bare coil from mains. If an iron core is introduced, record it as a changed condition because it changes the field and can obstruct some readings. Writing a method does not prove supervised practical competence.
Pause and explain
Why should a large compass not be forced into a small solenoid?
Worked example
How can a solenoid investigation distinguish a pole label from mere filings alignment?
Show the worked solution
- Observe alignment for the broad pattern.
- Use settled compass north-tip readings outside an end.
- A north end has field directed outward in the nearby external region.
Answer Use compass direction, not filings orientation alone, to identify pole sense.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Write a solenoid field method covering pattern and direction inside and outside.
Give me a hint
Use appropriate apparatus with accessible marked positions.
Compare my reasoning
- Fix a suitable solenoid in a low-voltage current-limited circuit.
- Observe filings for the broad pattern.
- Use compass north-tip readings along the axis and near the ends.
A controlled map of internal and external pattern and direction.
Look for these in your work
- Include both regions.
- Use a direction-sensitive indicator.
Explain why current-off and unchanged nearby-material controls matter.
Give me a hint
The compass aligns with the resultant local field.
Compare my reasoning
- Current-off identifies background.
- Magnetic materials can change field contributions.
- Fixed material and geometry support the current-on comparison.
Controls help isolate the solenoid contribution without claiming all other fields vanish.
Look for these in your work
- Identify confounding contributions.
- Keep limits explicit.
A comparison increases current and inserts an iron core, then attributes every observed change to current. Evaluate it.
Give me a hint
Count the deliberately changed factors.
Compare my reasoning
- The current changed.
- The core material also changed.
- The result cannot isolate current alone.
It changes two factors; retain the same core condition to isolate current.
Look for these in your work
- Name both factors.
- State a corrected comparison.
Common mistakes
- Map both inside and outside.
- Core changes are an additional factor.
- Do not treat a compass angle as a calibrated field magnitude.
What can you explain now?
Which internal arrow sense belongs to a specified right-N solenoid?
Compare with the explanation
Left to right, from S toward N
The central internal field continues from the south end toward the north end.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Plan separate pattern and direction observations with coil, core and background conditions controlled.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.