(a) What are magnetic field lines? How is the direction of magnetic field at a point in a magnetic field determined using field lines?
(b) Two circular coils ‘A’ and ‘B’ are placed close to each other. If the current in the coil ‘A’ is changed, will some current be induced in the coil ‘B’? Give reason.
(c) State ‘Fleming’s right hand rule”.
Answer:
(a)
Magnetic field lines are imaginary lines along which the north magnetic pole would move in a magnetic field.
The direction of a magnetic field at a point is determined by placing a small compass needle. The North pole of the compass indicates the direction of the magnetic field at that point.
(b)
As the current flows in coil A, a magnetic field is generated around it.
As the coil B is situated near coil A, it also experiences the magnetic field.
As the current in coil A changes, the magnetic field associated with it also changes.
Hence, the magnetic field around coil B also changes.
Due to change in magnetic field around the coil B, a current is induced in coil B.
(c)
Fleming’s right hand rule states that, if we stretch the thumb, forefinger and middle finger of the right hand so that they are perpendicular to each other, then
- Thumb represents the direction of motion of the conductor.
- Index finger represents the direction of the magnetic field.
- Middle finger shows the direction of the induced current.
