1.
A vertical wire carrying a current of 5A is
situated in a uniform horizontal magnetic field of 4x10-3 T.
Calculate the magnitude of the force on the wire if the length of the wire in
the field is 0.4m. Draw a sketch showing the direction of the force on the wire
when the current flows (i) upwards and (ii) downwards. 8x10-3N
2.
Calculate the force on a wire of length 0.1 m
carrying a current of 10A if it is (i) perpendicular, (ii) inclined at 300
(iii) parallel to a field of 1 x10-2 T 0.01N, 0.005N, 0N.
3.
The
diagram shows a simple current balance. The loop is balanced when no current
flows, and no masses are added. The straight part of the wire is 15cm long and
is crossed by a magnetic field of 2.0 x10-3 T. The current in the
wire is 1.0 A. What mass must be hung from the other side in order for the
system to balance? g=9.81 ms-2
31mg
4. A
metal wire 10m long lies east west on a wooden table. What pd would have to
applied to the ends of the wire, and in what direction, in order to make the
wire rise from the surface. Assume that the electrical connections to wire
cause no appreciable constraint.
(density of the metal = 1.0 x
104 kgm-3, resistivity of the metal = 2 x 10-8
Ωm, horizontal component of the earth’s magnetic field = 1.8 x 10-5
T, g = 9.81 Nkg-1) 1.1kV WàE
