Types of Magnets :
Artificial magnets:
These magnets are created by artificial means.
Iron ore which we know as magnetite has magnetic properties of attracting iron, cobalt an nickel. These are called
lodestones.
Types of Magnetic Substances:
- Ferro-magnets: These are special substances which are strongly magnetized by relatively weak magnetic fields. Iron, nickel and cobalt are familiar examples of this class.
- Para magnetic substances: These magnetic substances when placed in a strong magnetic field get magnetized in the same sense as the external field. Aluminium, chromium, copper sulphate and liquid oxygen are familiar examples.
- Diamagnetic Substances: These substances when placed in a magnetic field get weakly magnetized in a sense opposite to the applied field. A few examples are bismuth, antimony, gold, water, alcohol and hydrogen.
Magnetic Induction:
When a piece of soft iron or steel is brought close to strong bar magnet, it is magnetized. when an electric current is passed through an
insulated copper wire coil, the steel or soft iron placed in the in the coil becomes the magnet.
Electrical Meters:
The modest meter to sense electrical current is a
magnetic compass. Then there is one that has a compass in a coil of wires. When an electric current passes through the coil, each loop produces its effect on the needle so even a very small current can be detected. Such a current-indicating instrument is called a
galvanometer.
Ammeter and Voltmeter:
A galvanometer may be calibrated to measure current, in which case is called an ammeter, or it may be calibrated to measure
electrical potential(Volts), in which case is called
Voltmeter.
Electric Motors:
With a slight alteration in the design of the galvanometer, we can convert a
galvanometer into an electric motor. The change will have to be so that deflection makes a complete turn rather than a partial rotation. The key change is that the current in a motor is made to alter direction each time the coil makes a half rotation.
Electronic Induction in Everyday Technologies:
Electromagnetic is used all around us. When walking the upright coils in a security system at an airport, any metal you carry slightly alters the magnetic field in the coils. This change induces voltage, which sounds a beep or an alarm.when the magnetic strip of the back of a credit card is scanned, induced voltage pulses identify the card.
Magnetic field of the Earth:
The Earth has its own magnetic field which is similar to the field produced by a huge magnet at its centre. Its north pole lying towards the geographical south pole and the south pole towards the geographical north pole.
Magnetic strip on a credit card:
A
magnetic strip on a credit or debit card contains millions of tiny magnetic domains held together by resin binder. data is encoded in binary code. with zeros and ones distinguished by the frequency of domain reversals. It is quite amazing how quickly
your name pops up when a retailer swipes your card at a shop for charging payment for goods or services sold to you.
Power Plants and Electricity Generation:
Today, the energy to turn the turbine is still often delivered by steam. In traditional power plants, the water is heated to steam by burning fossil fuels. In nuclear power plants, the energy to heat water to make steam is supplied by
nuclear fission reactions.