The term ‘magnetic effect of electric current’means that an electric current flowing in a wire produces a magnetic field around it . A iron, steel, nickel and cobalt. A bar magnet is a Magnet is an object which attracts pieces of long, rectangular bar of uniform cross-section which attracts pieces of iron, steel, nickel and cobalt.

INTRODUCTION :-

The region surrounding a magnet , in which the force of magnet can be detected is said to have a magnetic field.

Magnetic field is a quantity that has both magnitude and direction ; as such it is a vector quantity.

The term is used for two distinct but closely related fields denoted by the symbols B and H, which are measured in units of tesla and amp per meter respectively in the SI.B is most commonly defined in terms of the Lorentz force it exerts on moving electric charges.

The curved lines along which the iron filings align themselves or the path along which the freely pivoted magnetic needle moves is called the field lines or magnetic lines of force.

The direction of the field is taken to be the direction in which a north pole of the compass needle moves inside it.

1. Magnetic field lines are closed curves.2. Magnetic field lines appear to start from N-pole and appear to end at the south pole.(within the magnet , they run from S- pole to N-north pole)3. Magnetic field lines repel each other.4. No two magnetic lines cut each other. ( If they intersect , a compass needle placed at the intersection has to point two different directions at the same time which is impossible.)

Earth's magnetic field, also known as the geomagnetic field, is the magnetic field that extends from the Earth's interior to where it meets the solar wind, a stream of charged particles emanating from the Sun. Its magnitude at the Earth's surface ranges from 25 to 65 microtesla (0.25 to 0.65 gauss). It is approximately the field of a magnetic dipole tilted at an angle of 10 degrees with respect to Earth's rotational axis, as if there were a bar magnet placed at that angle at the center of the Earth. Unlike a bar magnet, however, Earth's magnetic field changes over time because it is generated by a geodynamic (in Earth's case, the motion of molten iron alloys in its outer core).

1. A magnetic compass shows the presence and direction of the magnetic field around a straight length of current-carrying wire.

2. The current through a wire produces a magnetic field.

3. The shape of the magnetic field lines for a straight conductor is concentric circles.

4. These concentric circles become larger as we move away from the wire.

•When you wrap your right hand

around the straight conductor such

that the thumb points in the direction of

the current, the fingers will wrap

around the conductor in the direction

of the field lines of the magnetic field..

1. The magnetic field lines are near circular at the points where the current enters or leaves the card board

2. Within the space enclosed by the coil, the field lines are in same direction.

3. Near the centre of the coil, the magnetic lines are almost parallel to each other. Thus mag. Field near the centre of the coil may be considered uniform.

4. At the centre of the coil the plane of magnetic field lines is at right angle to the plane of the coil.

5. If there is a circular coil having n turns, the field produced is n times as large as that produced by a single turn ,as the current in each turn has the same direction and the field due to each turn add up.

o A coil of many circular turns of insulated copper wire wrapped closely in the shape of a cylinder is called a solenoid.

o A solenoid produces a magnetic field when electric current is passed through it.

o The pattern of the magnetic field lines around a current-carrying solenoid is similar to that of a bar magnet.

o One end of the solenoid is like a magnetic north pole while the other is like the south pole

o

The directions of the current, force, and magnetic field can be illustrated through a simple rule called Fleming’s left-hand rule, if the direction of current is at right angles to the direction of the magnetic field.

According to this rule, stretch the thumb, forefinger, and middle finger of your left hand such that they are mutually perpendicular.

The first finger points in the direction of the magnetic field and the second finger in the direction of the current, then the thumb will point in the direction of motion or the force acting on the conductor.

The motion of a magnet with respect to the coil produces an induced potential difference, which sets up an induced electric current in the circuit .This phenomena is called electromagnetic induction. This was first studied by English physicist Michael Faraday. In 1831, Faraday made an important breakthrough by discovering how a moving magnet can be used to generate electric currents.

GalvanometerA galvanometer measures the direction and relative strength of an electric current from the magnetic field it produces. The pointer remains at zero (the Centre of the scale) for zero current flowing through it. It can deflect either to the left or to the right of the zero mark depending on the direction of current.

Stretch the thumb, forefinger and middle finger of right hand so that they are perpendicular to each other, as shown in the figure. If the forefinger indicates the direction of the magnetic field and the thumb shows the direction of motion of conductor, then the middle finger will show the direction of induced current. This simple rule is called Fleming’s right-hand rule.

In our homes, we receive supply of electric power through a main supply, either supported through overhead electric poles or by underground cables. One of the wires in this supply, usually with red insulation cover, is called live wire. Another wire, with black insulation, is called neutral wire. In our country, the potential difference between the two is 220 V.A fuse in a circuit prevents damage to the appliances and the circuit due to overloading . overloading can occur when the live and the neutral wire come in direct contact.In such a situation, the current in the circuit abruptly increases. This is called short-circuiting.