The magnetic field lines inside a current carrying long solenoid are in the form of

The correct answer is parallel straight lines.

Key Points

• The magnetic field lines inside a solenoid are in the form of parallel straight lines. Hence, Option 4 is correct.
• This pattern of field lines inside the solenoid indicates that the strength of the magnetic field is the same at all points.
• When current passes through the wires, a magnetic field is produced.
• Solenoid behaves like a permanent bar magnet.
• Whose south and north poles are the ends from where magnetic field lines are coming in and out, respectively.

Important Points

• There are two types of solenoid: finite and infinite solenoid.
• A finite solenoid is the one whose length is finite and the infinite is the one whose length is infinite such that the end effects are negligible.
• The magnetic field lines are parallel to the axis of the long infinite solenoid and the magnetic field does not vary along the length.
• The magnetic field almost seems to be a straight line.
• A coil of many circular turns of insulated copper wire wrapped closely in a cylinder’s shape is called a solenoid.
• The field pattern is identical to that of a magnetic field around a bar magnet.
• The solenoid’s one end acts as a magnetic north pole, while the other acts as a magnetic south pole.
• Within the solenoid, the field lines are in the form of parallel straight lines.
• It means that the magnetic field within the solenoid is the same at all points.
• That is, the field within the solenoid is uniform.
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