Investigating the Field Around a Wire | Physics for GCSE/IGCSE - Year 11 PDF Download

Investigating the Field Around a Wire

• The investigation of magnetic field patterns resulting from currents in straight wires and solenoids involves the use of specific equipment and materials, such as:
  • A thick wire
  • A solenoid (a wire coiled into a spiral shape, similar to a metal slinky)
  • Necessary electrical components like a cell, ammeter, variable resistor, and connecting wires
  • Cardboard with appropriately sized holes to accommodate the wire
  • A clamp stand for stability
  • Iron filings or a compass for visualizing magnetic fields
• Spread the iron filings uniformly on the cardboard and place the magnetic needle on the board
• Tap the cardboard slightly and observe the orientation of iron filings

When the current changes direction, the compasses indicate the opposite direction, indicating that the field direction also switches when the current does.

Experiment 1: Plotting the magnetic field around a wire

• Attach the thick wire through a hole in the middle of the cardboard and secure it to the clamp stand
• Secure the wire vertically so it sits perpendicularly to the cardboard
• Attach the ends of the wire to a series circuit containing the variable resistor and ammeter on either side of the cell

Using plotting compasses:

• Place plotting compasses on the card and draw dots at each end of the needle once it settles
  • Make sure to draw an arrow to show the direction of the field at different points
• Make sure to indicate the direction of the field at various points.
• Move the compass away from each dot, repeating the process consistently.
• Continue this process until a sequence of dots is visible on the card.
• Remove the compass and connect the dots with a smooth curve to form a magnetic field line.
• Repeat the entire procedure multiple times to generate several magnetic field lines.

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Using Iron Filings:

• If iron filings are available, sprinkle them on the cards and gently shake the card until they align with the magnetic field pattern around the wire.

Experiment 2: Plotting the magnetic field around a solenoid

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Setting Up the Experiment:

• Thread a thick wire through one side of the cardboard, looping it through the other side and securing it with a clamp stand to form a circular loop.
• Connect the wire ends to a series circuit incorporating the variable resistor and ammeter on either side of the cell.

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Using Plotting Compasses:

• Follow the steps outlined in Experiment 1. 
  • Note: This can be performed with a solenoid, as the pattern around a circular loop can be extended to represent the pattern around a solenoid.

Using iron filings and a solenoid:

• Take a solenoid (you can also use a metal slinky) and pass it through pre-made holes in a piece of card.
• Sprinkle iron filings onto the card surface and gently tap or shake the card until the filings align in the pattern reflecting the magnetic field around the solenoid.