Magnetic effects of Electric Current Notes CBSE Class 10 Science
- A piece of loadstone can attract iron nails and when it is suspended freely it aligns in the north-south direction.
- A compass needle is a light bar magnet, whose north pole points towards geographic north approximately. Like poles of magnets repeal whereas unlike poles attract.
- The region or space around a magnet where magnetic force can be experienced by other magnetic substances is called magnetic field.
- If we face a coil such that current in the coil is in anticlockwise direction, then magnetic field will be towards us i.e. there will be a N-pole.
- If we face a coil such that current in the coil is in clockwise direction, then magnetic field will be away from us, i.e. there will be a S-pole
- A solenoid consists of many circular turns of an insulated wire in the shape of cylinder.
- Magnetic field due to a solenoid is directly proportional to (i) current through it, (ii) number of turns, (iii) magnetic permeability of material of core and (iv) inversely proportional to the length of solenoid.
- When soft iron and steel are placed inside strong magnetic field, these get magnetized. In case of soft iron magnetization is temporary whereas in case of steel it is permanent.
- A solenoid with soft iron is called an electromagnet. An electromagnet is a temporary magnet, its magnetism lasts as long as current flows through it.
- In the year 1831 Michael Faraday found that moving magnet with respect to a coil produce emf and current, which is called electromagnetic induction.
- Number of magnetic lines of force passing through a given area is called a magnetic flux.
- Whenever there is a relative motion between a coil and a magnet, magnetic flux passing through coil changes which results in induced emf and current.
- To avoid short-circuiting and overloading, wires of better quality insulation must be used. Another important prevention against overloading and short-circuiting is use of ‘Fuse’. Its a metallic wire of alloy of tin and lead (35% lead and 65% tin) with low melting point, whenever there is overloading and short-circuiting and current exceeds the tolerance limit ‘fuse’ melts and break the circuit and saves the other appliances.