Mgnetic Effect and Electric

Magnet A substance which has the property of attracting other substances like iron filings and points in the north south direction when suspended freely is called a magnet.

Magnetic field The space around a magnet in which the force of attraction and repulsion due to it can be detected is called the magnetic field.

Magnetic field lines The curved paths along which the north pole of the compass needle moves in a magnetic field are called magnetic field lines. Magnetic field lines are used to represent a magnetic field.

Properties of magnetic field lines

1. The magnetic field lines never intersect each other because if they do so it means that at that point the compass needle would point towards two directions which is not possible.
2. They emerge at North Pole and merge at South Pole.
3. They are crowded near the poles and are far apart near the middle.
4. These are directed from North Pole to South Pole outside the magnet and from south to North Pole inside the magnet.

Compass needle A compass needle is a small bar magnet whose ends always point towards north south direction. The end pointing towards north is called North Pole and the end pointing towards south is called South Pole.

Magnetic field due to a current carrying straight wire The straight current carrying conductor produces a magnetic field around it in the form of concentric circular field lines with the conductor at the centre.

Factors affecting strength of magnetic field around a current carrying straight conductor. Strength of magnetic field is directly proportional to the current passing through the conductor and inversely proportional to the distance from the conductor. ( B a I and B a 1/r )

Right hand thumb rule or Maxwell's clockwise rule If we hold a straight wire in our right hand, and if the thumb represents the direction of current then the fingers represent the direction of magnetic field lines.

Magnetic field due to current carrying circular loop or coilWhen the current is passed through circular loop or coil, the lines of force are circular near the wire but straight and parallel near the centre of loop or coil. Factors affecting magnetic field due to current carrying circular loop or coil.

Magnetic field due to current carrying circular loop at its centre is-

1. Directly proportional to the current passing through it.
2. Inversely proportional to the radius of loop.

Magnetic field due to current in a solenoid The Magnetic field due to current carrying solenoid is similar to the magnetic field produced by a bar magnet. The ends of the solenoid act as North Pole and South Pole. The field lines inside the solenoid are in the form of straight parallel lines.