Tutorial 3 Magnetism

With reference to permanent magnets, which of the following statements is true ?

• like poles repel each other

• like poles attract each other

• unlike poles repel each other

• none of the above.

With reference to a magnetic field, which of the following statements is true?

• lines of flux intersect each other

• lines of flux are most concentrated where the field is the weakest

• lines which are parallel and in the same direction attract each other

• lines of flux emerge from the north pole, enter through the south pole

  and continue to flow inside the bar magnet to form closed path

Answer explanation

• Lines of flux never intersect.

• Lines of flux are always continuous and form closed path.

• Lines of flux which are parallel and in the same direction repel each other.

• Lines of flux emerge from the north pole and enter through the south pole of a

bar magnet.

• Lines of flux are most concentrated where the field is the strongest.

• Lines of flux are like stretched elastic cords, always trying to shorten

themselves.

The flux density of a magnetic field :

• depends only on the area in the field

• depends only on the flux in the field

• represents the strength of the field

• represents the direction of the field.

When an electric current flows through a straight conductor, a magnetic field

with the following pattern is set up :

• a pattern similar to that of a bar magnet

• lines of flux in concentric circles

• irregular pattern

• lines of flux in parallel

Answer explanation

The pattern of the magnetic field produced by a current-carrying conductor can be

plotted. The lines of magnetic flux is in the form of concentric circles around the

conductor.

The basic unit of flux density is

The basic unit magnetic flux is

The Right Hand Grip Rule is used to determine :

• direction of induced e.m.f.

• direction of force acting on a conductor

• direction of lines of magnetic flux around a current-carrying conductor

• none of the above.

Label North and South

If the solenoid is gripped with the right hand, with the fingers pointing in the direction of the

_______; then the thumb, placed along the axis, will point in the direction of the north

pole.

Fleming’s Left Hand Rule is used to determine the direction of

• e.m.f. induced in a conductor moving across a magnetic field

• the force acting on a current-carrying conductor lying in a magnetic

  field

• the magnetic field around a current-carrying conductor

• the magnetic field set up by a current-carrying solenoid