A Danish scientist Hans Christian Oersted for the first time in 1819 discovered that when an electric current is passed through any conductor, a magnetic field is produced around it. Magnetic Effects of Electric Current Oersted Experiment

The region around a magnet where its influence can be felt is called its magnetic field. Magnetic field cannot be seen, but it can be traced by plotting magnetic lines of force (or magnetic field lines) with the help of a compass needle or by sprinkling iron filings around it. Magnetic Effects of Electric Current Magnetic Field

A magnetic compass or compass needle is a small/light magnetic needle (or pointer) pivoted at its centre in a small aluminium/brass case with a glass top. The pointed end of the pointer indicates the north direction. Magnetic Effects of Electric Current Magnetic Compass

A compass needle is placed near to the north pole (N) of the magnet. The north pole of the compass needle stays away from the N-pole of the magnet because like poles repel each other. Magnetic Effects of Electric Current Magnetic Field Lines

Mark the position of the north pole of the compass needle on the paper with a pencil. Shift the compass needle so that its south pole coincides with the dot marked on the paper. Then join all these pencil dots. The curve so obtained is called the magnetic line of force. Magnetic Effects of Electric Current Magnetic Field Lines

Magnetic Effects of Electric Current Properties of Magnetic Field Lines (i)Magnetic field lines start at the N-pole and end at the south pole. (ii) Magnetic field lines do not intersect each other. (iii) The degree of closeness of the field lines depends upon the strength of the magnetic field. Stronger the field, closer are the field lines.

Magnetic Effects of Electric Current Magnetic Field If a magnetic compass is placed near a conductor carrying current (wire), the needle is deflected. This shows that a conductor carrying current has a magnetic field around it. If the direction of the current is from north to south, the deflection of the magnetic needle is towards the east. MAGNETIC FIELD DUE TO A CURRENT-CARRYING CONDUCTOR

Magnetic Effects of Electric Current Magnetic Field If the direction of the current is from south to north, the deflection of the needle is towards the west.

Magnetic Effects of Electric Current Magnetic Field The magnetic field around a current carrying straight conductor is in concentric circles. It can be observed by passing a current carrying straight conductor through a cardboard and sprinkling iron filings on it. MAGNETIC FIELD DUE TO A CURRENT THROUGH A STRAIGHT CONDUCTOR

Magnetic Effects of Electric Current Right Hand Thumb Rule The direction of the magnetic field around a conductor is given by the Right Hand Thumb Rule. It states that ‘ If a current carrying conductor is held in the right hand such that the thumb points in the direction of current, then the fingers wrapped around the conductor shows the direction of the magnetic field ’.

Magnetic Effects of Electric Current Magnetic field When current is passed through a circular conductor (loop) the magnetic field produced is in the form of concentric circles around the conductor. Towards the centre the arcs of the circles become larger and appears as straight line. MAGNETIC FIELD DUE TO A CURRENT THROUGH A CIRCULAR LOOP

Magnetic Effects of Electric Current Magnetic Field A solenoid is a circular coil of wire in the shape of a cylinder. When current flows through a solenoid, it behaves like a bar magnet. The ends of the solenoid behaves like the North and South poles of a magnet. MAGNETIC FIELD DUE TO A CURRENT IN A SOLENOID

Magnetic Effects of Electric Current Magnetic Field The strength of the magnetic field depends upon the strength of the current and the number of turns of the coil. The magnetic field produced by a solenoid is similar to the magnetic field produced by a bar magnet.