Method

1. Setup the Circuit and Zero the Balance:

• Arrange the apparatus as shown, ensuring the wire is positioned horizontally between the two magnets and can move freely within the magnetic field.
• With no current flowing, tare the balance to zero the mass reading.

2. Apply Current and Record Force:

• Adjust the power supply to set the current $I$ to 0.50 A, as measured by the ammeter.
• Record the mass $m$ displayed on the balance. This change in mass reflects the downward force acting on the wire.

3. Increase Current:

• Increase the current in increments of 0.50 A, repeating the measurements up to a maximum current of 6.0 A.
• For each current setting, record the mass on the balance.

4. Repeat for Accuracy:

• Conduct the experiment twice more to obtain average mass readings for each current.

5. Measure Length of Wire in Field:

• Use the ruler to measure the length $L$ of the wire within the magnetic field (i.e., the distance between the two magnets).

Safety

• Avoid Touching the Wire: High currents can cause the wire to heat up, which may result in burns.
• Ensure Equipment Stability: Make sure the setup is secure to prevent any components from tipping or falling due to the applied magnetic force.

Key Concepts

• Magnetic Force on a Wire: The force on a current-carrying wire in a magnetic field depends on the magnetic flux density $B$, the current $I$, and the length of wire $L$ in the field.
• Calculating Flux Density: By measuring force at different currents and plotting $F$ against $I$, we can determine $B$ from the graph's gradient.
• Practical Application of $F = BIL$: This experiment demonstrates the quantitative relationship between magnetic fields and electric currents, a fundamental concept in electromagnetism.