PHY_10_3_V2_DM2_Measuring magnetic flux density

(f) Formative assessment.

The diagram shows an arrangement that is used to determine the magnetic flux density
between the poles of a magnet.

The magnet is placed on a sensitive top pan balance. A current-carrying wire is placed at right angles to the magnetic field between the poles of the magnet. The force experienced by the current-carrying wire is equal but opposite to the force experienced by the magnet. The magnet
is pushed downward when the wire experiences an upward force.

The length of the wire in the magnetic field is 5.0 cm. The balance reading is 102.00 g when
there is no current in the wire. The balance reading increases to 103.14 g when the current in
the wire is 8.2 A.

a    Show that the force experienced by the wire is equal to 1.1 ´ 10⁻² N.

 [1]

b    Calculate the magnetic flux density of the magnetic field between the poles of the magnet.                                                                                                                                                                                                                      

[3]