SOLENOID
A coil of many circular turns of insulated copper wire wrapped closely in the form of a cylinder is called a solenoid.
| A solenoid |
MAGNETIC FIELD DUE TO CURRENT IN A SOLENOID
1. The magnetic field due to a solenoid is very much similar to that of a bar magnet. The pattern of the magnetic field lines around a current-carrying solenoid is similar to that of bar magnet. Just like a bar magnet, one end of the solenoid behaves as a magnetic north pole, while the other behaves as the South Pole.
2. The field lines inside the solenoid are in the form of parallel straight lines. This indicates that the magnetic field is the same at all points inside the solenoid. That is, the field is uniform inside the solenoid.
2. The field lines inside the solenoid are in the form of parallel straight lines. This indicates that the magnetic field is the same at all points inside the solenoid. That is, the field is uniform inside the solenoid.
PRACTICAL USE OF SOLENOID
A strong magnetic field produced in a solenoid can be used to magnetize a piece of magnetic material when it is placed within the coil, which is carrying electric current.
ACTIVITY
1. Take a iron nail.
2. Wrap a coil of insulated copper wire on it.
3. Connect the coil to a battery through a switch.
4. As the current is passed through the coil, the nail, which acts as a core inside the solenoid, gets magnetized.
The magnet so formed is called an electromagnet.
ELECTROMAGNET
An electromagnet consists of a long coil of insulated copper wire wound on a soft iron core.
TEMPORARY MAGNET
If the core of the solenoid is taken of soft iron and electric current is passed through the solenoid, the soft iron core is temporarily magnetized which means when the current is switched off soft iron loses its magnetic properties. An electromagnet is a temporary magnet.
PERMANENT MAGNET
If the core of the solenoid is taken of carbon steel, chromium steel, cobalt and tungsten steel and certain alloys like Nipermag (alloy of iron, nickel, aluminium and titanium) and ALNICO (alloy of Aluminium, nickel and cobalt) and a strong electric current is passed through the coil then these materials become permanently magnetized.
Such permanent magnets are used in microphones, loudspeakers, electric clocks, ammeter, voltmeter and speedometer, etc.
Uses of permanent magnets
Such permanent magnets are used in microphones, loudspeakers, electric clocks, ammeter, voltmeter and speedometer, etc.
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