objecti
To
field lines around astraight
plot magnetic field
current-carrying wire with a
compass
Apparatus
Straight wire, plotting compass, cardboard, pencil.
e.m.f. source
Procedure
1. Thread a wire through asmall hole in a sheet of
cardboard. The wire should be perpendicular to
the cardboard sheet (Figure 21.2). Connect the
wire to an e.mn.f. source such that the current
flows up the wire.
2. Place acompass on the cardboard sheet.
3. On the cardboard sheet, mark the positions of
the S and N ends of the compass needle with
pencil dots X and Y respectively.
4. Move the compass so that the S end of the
needle is now at Y(Figure 21.3).
5. Mark the new position of the N end of the needle
with a third dot Z.
6. Repeat steps 2 to 5, placing the compass at
different distances from the wire until several
field lines are drawn.
Observation and Discussion
" The magnetic field plot obtained consisted of
concentric circles (Figure 21.4).
The circles nearer the wire were closer tO one
another. This implies that the magnetic field was
stronger at regions nearer the wire.