Graphs of Potential Difference in the Coil (OCR GCSE Physics A (Gateway Science Suite)): Revision Notes

When a coil rotates within a magnetic field, it experiences a changing magnetic flux, which induces a potential difference across its ends.

How to Draw the Graph

1. Setting Up the Axes:

• On graph paper, label the horizontal axis as "Time (s)" and the vertical axis as "Potential Difference (V)".
• Ensure you choose appropriate scales for both axes to accurately plot the data.

2. Collecting Data:

• As the coil rotates, determine the potential difference at various time intervals. This will depend on factors like the speed of rotation, magnetic field strength, and the number of turns in the coil.

3. Plotting the Points:

• For each time interval, plot the corresponding potential difference on the graph. Repeat this for multiple intervals to capture the full cycle of rotation.

4. Drawing the Curve:

• Connect the plotted points with a smooth curve. This curve shows how the potential difference changes over time as the coil rotates.

Interpreting the Graph Once the graph is drawn, interpreting it gives you insights into the behaviour of the potential difference:

5. Starting Point:

• The graph starts at the origin (0 V) because no potential difference is generated when the coil is stationary.

6. Shape of the Curve:

• The curve's shape depends on the coil's rotation speed and the magnetic field's strength. Typically, the potential difference increases as the coil rotates, peaks when the coil is perpendicular to the magnetic field lines, and then decreases.

7. Periodic Variation:

• If the coil makes multiple rotations, the graph will show a repeating pattern. The potential difference will rise and fall in a cyclical manner, reflecting the continuous rotation of the coil.

8. Maximum Potential Difference:

• The highest points on the graph represent the maximum potential difference, which occurs when the coil is aligned perpendicularly to the magnetic field.

9. Direction of Potential Difference:

• The potential difference may change direction (sign) depending on the rotation direction of the coil. This is reflected in the graph by the curve crossing the horizontal axis (indicating a switch from positive to negative voltage or vice versa).