CHSE MAGNETIC EFFECTS OF ELECTRIC CURRENT

Chse magnetic effect of current notes and Important questions

Chse +2 magnetic effect of current|magnetic effect of current class 12 chse|chse Physics notes|+2 2nd year notes Science|

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Key points 

What is a Magnet?

A magnet is defined as an object which is capable of producing magnetic field and attracting unlike poles and repelling like poles.

Use of Magnets: Magnets are used

-refrigerators.

-in radio and stereo speakers.

-in audio and video cassette players.

-in children’s toys and;

-on hard discs and floppies of computers.

Properties of Magnet:

-A free suspended magnet always points towards the north and south direction.

-The pole of a magnet which points toward north direction is called north pole or north-seeking.

-The pole of a magnet which points toward south direction is called south pole or south seeking.

-Like poles of magnets repel each other while unlike poles of magnets attract each other.

Oersted experiment

Oersted discovered a magnetic field around a conductor carrying electric current. Other related facts are as follows:

(a) A magnet at rest produces a magnetic field around it while an electric charge at  rest produce an electric field around it.

(b) A current carrying conductor has a magnetic field and not an electric field around it. On the other hand, a charge moving with a uniform velocity has an electric as well as a magnetic field around it.

(c) An electric field cannot be produced without a charge whereas a magnetic field can be produced without a magnet.

(d) No poles are produced in a coil carrying current but such a coil shows north and south polarities.

(e) All oscillating or an accelerated charge produces E.M. waves also in additions to electric and magnetic fields.

Magnetic field: The area around a magnet where a magnetic force is experienced is called the magnetic field.

Or The influence of force surrounding a magnet is called magnetic field. In the magnetic field, the force exerted by a magnet can be detected using a compass or any other magnet.

- It is a quantity that has both direction and magnitude, (i.e., Vector quantity).

-SI unit of magnetic field is Wm-² or (tesla) 

Properties of magnetic field

-The magnitude of magnetic field increases with increase in electric current and decreases with decrease in electric current.

-The magnitude of magnetic field produced by electric current decreases with increase in distance and vice – versa. The size of concentric circles of magnetic field lines increases with distance from the conductor, which shows that magnetic field decreases with distance.

-Magnetic field lines are always parallel to each other.

-No two field lines cross each other.

Magnetic field lines : The imaginary lines of magnetic field around a magnet are called field line or field line of magnet. When iron fillings are allowed to settle around a bar magnet, they get arranged in a pattern which mimicks the magnetic field lines. Field line of a magnet can also be detected using a compass. Magnetic field is a vector quantity, i.e. it has both direction and magnitude.

Direction of field line: Outside the magnet, the direction of magnetic field line is taken from North pole to South Pole. Inside the magnet, the direction of magnetic field line is taken from South pole to North pole.

Strength of magnetic field: The closeness of field lines shows the relative strength of magnetic field, i.e. closer lines show stronger magnetic field and vice – versa. Crowded field lines near the poles of magnet show more strength.

Properties of magnetic field lines.               (i) They do not intersect each other.                (ii) It is taken by convention that magnetic field lines emerge from North pole and merge at the South pole. Inside the magnet, their direction is from South pole to North pole. Therefore magnetic field lines are closed curves.

Ampere’s Swimming Rule  if a man is swimming s along the wire in the direction of current his face turned towards the needle, so that the current enters through his feet, then north pole of the magnetic needle will be deflected towards his left hand.

Ammeter

An ammeter is a low resistance galvanometer used for measuring the current in a circuit.

It is always connected in series.

Voltmeter

A voltmeter is a high resistance galvanometer used for measuring the potential difference between two points.

-It is always connected in parallel.

-The resistance of an ideal voltmeter is infinity.

Magnetic induction:- A magnet induces magnetism in a magnetic substance placed near it. This phenomenon is called magnetic induction.

Fleming’s left Hand Rule

If we stretch the thumb, the forefinger and the central finger if left hand in such a way that all three are perpendicular to each other, then if forefinger represents the direction of magnetic field, central finger represents the direction of current flowing through the conductor, then thumb will represent the direction of magnetic force.

Magnetic dipole:- An arrangement of two equal and opposite magnetic poles separated by a small distance is called a magnetic dipole.

Magnetic dipole moment:- It is defined as the product of its pole strength and magnetic length. 

Gauss’s Law for Magnetism: It states that the net magnet flux through any closed surface is zero.

Cyclotron Cyclotron is a device used to accelerate positively charged particles such as proton, deuteron etc.

Principle of Cyclotron

A positively charged particle can be accelerated through a modera. electric field by crossing it again and again by use of strong magnetic field.

Moving Coil Galvanometer

It is a device used for the detection and measurement of the currents.In equilibrium, deflecting torque = restoring torque

Solenoid

A solenoid is a closely wound helix of insulated copper wire.

Elements of the Earth’s Magnetic Field: Three quantities are needed to specify the magnetic field of the earth on its surface-

a) The horizontal component of earth’s magnetic field (BH)- It is the component of the earth’s total magnetic field  in the horizontal direction in the magnetic meridian.

b) The magnetic declination - The angle between the geographic meridian and the magnetic meridian at a place is called the magnetic declination at that place.

c) The angle of dip or magnetic inclination -The angle made by the earth’s total magnetic field  with the horizontal direction in the magnetic meridian is called angle of dip at any place.

Magnetic Intensity or Magnetising field intensity:- The ability of magnetising field to magnetise a material medium. Let a material placed in an external magnetic field  , The magnetic intensity is, 

Magnetic induction:- It is defined as the total number of magnetic lines of force crossing per unit area normally through a material.

Intensity of magnetization :- It is defined as the dipole moment per unit volume , then the magnetic field  in the material will be-

Magnetic permeability ( :- It is defined as the ratio of its magnetic induction B to the magnetic intensity H. 

Relative permeability :- It is defined as the ratio of the permeability of the medium to the permeability of free space.

Magnetic susceptibility :- It is defined as the ratio of the intensity of magnetisation M to the magnetising field intensity .

Classification of Magnetic Materials: Magnetic materials are broadly classified as-

a) Diamagnetic- Those substances which develope feeble magnetisation in the opposite direction of the magnetising field. Examples- Bismuth, Copper, Lead, Zinc etc.

b) Paramagnetic- Those substances which develope feeble magnetisation in the direction of the magnetising field. Examples- Aluminium, Chromium, Platinum etc.

c) Ferromagnetic- Those substances which develope strong magnetisation in the direction of the magnetising field. Examples- Iron, Nickle, Cobalt etc.