Which one of these statements is true for a magnetic field?
Between two poles of a magnet, the field is uniform, but from a single pole the field is radial.
It is not possible to make a truly radial magnetic field, because magnets are always dipoles.
A truly radial field can be made using carefully shaped pole pieces.
A truly radial field can be observed when looking at a magnet end-on.
Which one of these correctly describes the relationship between the flux density and the distance?
B
µ
r
B
µ
r^{2}
B
µ 1/r
B
µ
1/r^{2}
Which one of these statements is correct about the force on a current carrying wire in a magnetic field?
The wire has to be made out of a magnetic material.
The maximum force is measured when the wire is parallel to the magnetic field.
The force is the same whatever the angle the wire makes to the magnetic field.
The maximum force is measured when the wire is at 90 degrees to the magnetic field.
The direction of movement of a wire in a magnetic field is determined by:
Fleming's Right Hand Rule
Fleming's Left Hand Rule
Faraday's Law
Lenz's Law
A current of 5.0 A is flowing at an angle of 30 degrees to a magnetic field of flux density 4.5 mT. The length of the wire in the field is 12 cm. What is the force acting on the wire?
1.35 × 10-3 N
2.3 × 10-3 N
2.7 × 10-3 N
1.35 N
Two wires are parallel to each other for a distance of 1.25 m and are 5 cm apart. One wire carries a current of 5.0 A upwards, while the other carries a current of 3.5 A downwards.
8.75 × 10-7 N, attractive
8.75 × 10-7 N, repulsive
8.75 × 10-5 N, attractive
8.75 × 10-5 N, repulsive
Which one of these is correct for how the force from an electromagnet is linked to the current?
F
µ
I^{2}
F
µ I
F
µ
1/I^{2}
F
µ
1/I
Which one of these factors is most likely to be a limiting factor on the strength of an electromagnet?
The current.
The permeability of free space.
The permittivity of free space.
The saturation of the material that makes the core.
Which one of these designs will make the most powerful electromagnet for a specified current?
A core of square cross section, 10 cm × 10 cm, 1200 turns, length 2 cm.
A core of circular cross section, 10 cm in diameter, 1200 turns, length 2 cm.
A core of square cross section, 10 cm × 10 cm, 1200 turns, length 20 cm.
A core of circular cross section, 10 cm in diameter, 2000 turns, length 20 cm.
Which one of these relationships correctly describes the relationship between flux and the force of an electromagnet?