Magnetic Field: distance and current

You will investigate a specific question: how does magnetic field change when the sensor moves closer to a current-carrying conductor, and what happens when current is larger?

Before opening the lab, use this vocabulary:

- Electric current: ordered movement of charge. In this activity it is measured in amperes, A.
- Conductor: a material that lets current flow. Here it is a straight conductor, similar to a wire.
- Magnetic field, B: magnetic effect around the conductor. The screen reads it in millitesla, mT.
- Hall sensor: a sensor that measures the magnetic field at its position.
- Distance, r: separation between the Hall sensor and the conductor. The screen reads it in centimeters, cm.
- Controlled comparison: a fair comparison where only one important variable changes. To compare currents, use equal or very similar distances.
- Outlier: a data point that is very different from nearby data. Do not delete it without explanation; flag it and review it.

A straight conductor carrying electric current creates a magnetic field around it. In this lab, a Hall sensor moves closer to the conductor while current stays fixed during the run. Your job is not to prove a perfect formula: it is to use real data to defend a pattern and recognize limits.

In this activity you will follow one concrete route: run 4 A in the lab and record rows from the trace while the sensor moves. Then compare that observation with labelled reference rows for other currents. The lab does not let you type any distance you want, so your comparison must use similar distance rows, not invented points.

Open the lab, observe one 4 A run, and record data. You do not need to download anything from the lab to complete this activity: copy the visible rows you need by hand.

Use the following reference rows to compare currents with a common class route. Copy the rows you need into your evidence table and write reference in the "Run/source" column. Do not mix them in as if you observed them live yourself.

Reference rows you may copy:
- 4 A: 20 cm -> 0.0041 mT; 10 cm -> 0.0092 mT; 5 cm -> 0.0182 mT; 2 cm -> 0.0382 mT.
- 8 A: 20 cm -> 0.0080 mT; 10 cm -> 0.0165 mT; 5 cm -> 0.0333 mT; 2 cm -> 0.0796 mT.
- 12 A: 20 cm -> 0.0107 mT; 10 cm -> 0.0249 mT; 5 cm -> 0.0470 mT; 2 cm -> 0.1108 mT.
- 16 A: 20 cm -> 0.0140 mT; 10 cm -> 0.0311 mT; 5 cm -> 0.0624 mT; 2 cm -> 0.1332 mT.

Now fill your evidence table. Each row represents one distance for one current. Copy current_a, distance_cm, and magnetic_field_mt from the lab or reference rows; calculate distance_m by dividing cm by 100; calculate inverse_distance_m_inv as 1 / distance_m; and complete source_or_repeat with observed 4 A, observed 8 A, reference, or another clear label. Use the notes column if a row looks like a possible outlier.

For the graph, 1/r means "one divided by the distance in meters". You do not have to prove a formula: use it as a simple way to check whether points closer to the conductor have a larger field than points farther away.

Graphs make the pattern easier to see without memorizing a formula. First compare B with distance for your 4 A observation. Then compare B at similar distances for several currents using the labelled reference rows. If you make a 1/r graph, use it only as a guide: the real lab does not have to produce a perfect line.

Now write a conclusion that a physics teacher could assess quickly. Use claim, evidence, reasoning, and uncertainty.

Use this only if your teacher assigns the longer version.