Magnetic effect of electric current class 10 notes|| class 10 magnetism notes ||class 10 chapter 13 notes||
MAGNETIC EFFECT OF ELECTRIC CURRENT
{It means that electric current produces magnetism}
Topics To Be Covered-
- What do you mean by the name of chapter
- What is magnet and it's properties.
- Magnetic field
- Magnetic field lines and it's properties.
- Oersted's experment.
- Magnetic field due to a current carrying conductor.
- Magnetic field due to a current through a straight conductor.
- Ampere's swimming rule.
- Snow rule.
- Maxwell's Right hand thumb rule.
- Magnetic field due to a current through a circular loop.
- Clock face rule.
- Magnetic field due to a current in a solenoid.
- Force on a current carrying conductor in a magnetic field.
- The kicking wire experiment.
- Fleming's left hand rule.
- Magnetism in human being.
- Electric motor.
- Electromagnetic induction.
- Fleming's Right hand thumb rule.
- Lenz 's law.
- AC generator.
- DC generator.
- Domestic electric circuit.
- Difference between AC and DC Generator.
MAGNET:
- It is an object which attract or repel the pieces of iron , steel etc.
- e.g- Bar magnet,Horshoe magnet,compass magnet ect.
Properties:
- The magnet always exist in dipole(north and south).
- Like poles repel and unlike poles attract each other.
- when a magnet freely suspended, it always allies towards north direction
- The two poles of the magnet cannot be separated.
- The magnetic field is the area around a magnet in which the magnetic force can be experienced by other ferromagnetic material. Or-
- Magnet develop certain area around it where its effect can be felt is known as magnetic field.
- The SI unit of magnetic field is- Tesla or weber/ meter square.
- CGS unit - Gauss(G).
- Magnetic field lines are the imaginary lines used to represent the magnetic field around a magnetic substance.
- Magnetic field line = magnetic line of force.
- The magnetic field lines originate from north pole and terminate at South Pole
- Inside the magnet the direction of feed line is from South Pole to North Pole.
- Magnetic field lines are always closed curves.
- Magnetic field lines are crowded near poles and they are widely separated at other places.
- When magnetic field lines are closer together it indicates is stronger magnetic field.
- When magnetic field lines are widely separated it indicate weak magnetic field.
- The to feed lines never cross each other as the two direction at a single point of intersection cannot occur at the same time
Oersted's Experment:
- It was given by Hans Christian oersted.
- He observed that magnetic effect in a compass placed nearby when the electric current is passed through the circuit.
- The unit of magnetic field strength is - (OERSTED).
Magnetic field due to a current carrying conducter:
- Take a long straight copper wire, two or three cells, plug key connected it in series.
- If the current flow from north to south then the needle deflected towards east.
- If the current flow from South to North then the needle deflected towards west.
- Therefore, it means that the direction of magnetic field produced by electric current is also reversed.
Magnetic field due to a current through a straight conductor:
- When the current is passed through the straight conductor the magnetic field lines around it is in the form of a concentric circles.
- These concentric circle represent the magnetic field lines.
- Magnitude of magnetic field lines is directly proportional to the current.
- If the current increases the magnetic field line also increases and vice- versa.
- If the direction of current reversed then the direction of magnetic field lines is also reversed.
Ampere 's Swimming Rule:
- Suppose a person is swimming in the direction of current such that the current enters the man throw his feet and leaves his body through head then the magnetic needle kept below it will get deflected what is left hand.
Snow Rule:
- It says that when the current flow from South to north direction the needle deflect towards west direction.
- when the current flow from north to south direction the needle deflect what east direction.
- According to it , imagine the straight conductor in your right hand such that the thumb points in the direction of current the direction of curl of fingers of the right hand give the direction of magnetic field lines
Magnetic field due to a current through a circular loop:
- When the current is passed through a circular loop of wire a magnetic field is produced around it.
- The magnetic field is circular as we move away from loop the concentric circle become larger.
- The magnetic field lines are circular at the point from their current enters or leaves.
- Within the space enclosed by a coil the field lines are in the same direction.
- Near the centre of the coil the magnetic field lines are almost parallel to each other and the strength of magnetic field lines also increases.
- At the centre of the coil the plane of magnetic field lines at the right angle to the plane of coil.
- Magnetic field is directly proportional to current and inversely proportional to distance.
- If there are (n) turns in a circular coil then the field produced is (n) times as large as that produced by a single turn.
- This is because the current in each circular turn has the same direction and the field due to each turn then just add up.
- Magnetic field is directly proportional to number of turns.
- By increasing the number of turns of wire.
- By increasing the current.
- By decreasing the radius.
Clock Face Rule:
- It is used to determine the polarity of two faces [ South or north] of a current carrying solenoid or electromagnet.
- Current-clockwise={South Pole}
- Current-Anticlockwise={North Pole}
- When the current is passed through solenoid it produces magnetic field which similar to magnetic field produced by bar magnet.
- One side of solenoid act as a North Pole and other side act a South Pole.
- The magnetic field inside the solenoid is in the form of parallel straight lines this indicate that strength of magnetic field inside the solenoid is same. [i.e uniform magnetic field].
- Number of turns in a solenoid. If turns increases-magnetic field increases.
- Strength of current. If Current increases- magnetic field increases.
- Nature of core material.
- Gap between turns of copper wire. If gap increases- magnetic field increases. If gap decrease- magnetic field decrease.
Electromagnet:
-It is a strong temporary magnet which consists of a long coil of copper wire wanted on a soft iron core.
-It is start behaving as a magnet only when the current is passed through it but as current is switched off the magnetism is lost
Factors affecting strength of electromagnet-
- Number of turns in a coil.
- Current flowing in it.
- Length of gap between poles.
Force on a current carrying conductor in a magnetic field:
-We know that if current is flowing in a conductor then it produces magnetic field.
-The field produced by the conductor exert a force on a magnet placed in the vicinity of the conductor.
MICHAEL FARADAY:
-When the current carrying conductor is placed in the magnetic field a mechanical force is exerted on the conductor which can make the conductor to move. This is known as MOTER PRINCIPAL.
The kicking wire experiment:
- When the current carrying conductor is placed in magnetic field a mechanical force exerted on the conductor to move.
- The direction of magnetic field current and force is mutually perpendicular to each other.
- The direction of the force on the conductor depend upon the direction of current and the direction of magnetic field.
-According to it -stretched the thumb forefinger and middle finger of your left hand such that they are mutually perpendicular. Then the thumb represent the direction of force, the forefinger represent a magnetic field and the middle finger represent direction of Current.
Note- The commutator is a device that reverse the direction of flow of current through the circuit. Split ring act as a commutator.
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Direction of induced Current
Difference between AC and DC current.
Magnetism in human beings:
- In our body extremely we electric current is produced by the moving of ions produces magnetic field.
- The two main organ where the magnetic field is significant is brain and heart.
- The magnetic field inside the body forms the basis of obtain image of the body parts are done using a technique MRI (magnetic resonance imaging).
Electric Motor:
-It is a device which convert electrical energy into mechanical energy.
Principal- When a rectangular coil carrying current is placed in magnetic field it experiences the force that rotate it.
Working-
- Imagine coil ABCD is in horizontal plane such that magnetic field is parallel to the plane of the coil.
- When electric current is passed through A to B then, by applying Fleming's left hand rule we come to know that it experience a force in upward direction C to D.
- When the coil turns 90 degree the commutator loses contact with brushesand does not force acting on the coil . but due to the momentum gain coil continue rotating till it cover 180 degree.
- After 180 degree it connect with brushes again and the current is now rivers to DCBA.
- This is how the electric motor work.
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The speed of rotation of the motor can be increased by:
- Increasing the strength of current through the armature.
- Increasing the number of turns in the coil of the armature.
- Increasing the area of coil.
- Increasing the strength of magnetic field.
-The production of electricity from magnetism.
- It is the used in electric generator for generating electricity.
Faraday's experiment:
- The experimental arrangement used by Faraday consists of a coil of n turns, a sensitive galvanometer connected in series with the coil. Faraday observe the following points.
- When the magnet is stationary, there is no deflection in galvanometer.
- When the north pole of magnet is brought toward the coil , a current flow in the coil and the galvanometer shows the deflected towards right.
- If the motion of the magnet is stopped the galvanometer again shows no deflection.
- If the magnet is moved away from the coil, the current flow in the direction opposite to the first direction.
- Exactly similar observations are made, if the magnet is stationary and the coil is moved either towards or away from the magnet.
- By increasing strength of magnet.
- By increasing the speed of rotation of coil or magnet.
- By increasing number of turns in a coil.
- By Changing the magnetic field.
- By Changing the area of the coil.
- By Changing the orientation of coil.
-Stretch your forefinger, centre finger and thumb mutually perpendicular to each other. such that the fore finger point in the direction of magnetic field ,the thumb point direction of motion and the centre finger indicate the direction of induced current.
Lenz's Law:
-The direction of current induced in a conductor by changing the magnetic field is such that the magnetic field created by the induced current opposes the initial changing magnetic field.
Experiment-
Case1: When (k) key is closed.
-Current in primary coil increases.
-Magnetic field increases in coil 1 and 2.
-Current in secondary coil is increases.
Case2: When (k) key is steady close.
-Current in primary coil is constant.
-Magnetic field is constant in both coil.
-Current in secondary coil is zero.
Case 3: when k key is just opened.
-Vurrent in primary coil decreases.
-Magnetic field decreases in both coil.
-Current in secondary coil decreases.
AC GENERATOR
{Alternating current generator}
-An AC generator converts mechanical energy into electric energy in the form ofb
alternating current or AC.
Principal- It is based on electromagnetic induction. when a closed coil is rotated with constant angular velocity in a uniform magnetic field with its Axis perpendicular to the magnetic field ,the magnetic field lines linked with the coil change. It induces and electromotive force between the end of the coil because of which induced current is produced. The direction of induced current in each arm of the coil is given by Fleming's right hand rule.
Working-
- Suppose initially the plane of armature coil ABCD is parallel to the magnetic field. Or its axis is perpendicular to the magnetic field.
- By doing some external mechanical work suppose the coil is rotated clockwise.
- In the first half rotation-
-The magnetic flux linked with the coil changes.
-According to the Fleming's right hand rule, induced current flow in the arm AB from A to B and in CD from C to D. Thus,the induced current will flow along ABCD.
-The induced current in the external circuit flow from B2 to B1.
- In the next half rotation.
-Now the direction of induced current in AB is inwards, B to A and in CD is D to C.
-Thus,induced current now flow in reverse direction i.e from DCBA.
-The current in the external circuit close from B1 to B2.
- After every rotation the direction of induced current changes.
- Such current which changes its direction after equal intervals of time is called an alternating current or AC.
DC GENERATOR:
[Direct current generator}
- If we replace the slip rings of AC generator by commutator then it will become a DC generator.
- In DC Generator split ring type commutator is used .
- When the two half ring of commutator are connected to the to end of a generator coil, than one carbon brush is at all times in contact with the coil arm moving down in magnetic field. while the other carbon brush always remain in contact with the coil are moving up magnetic field , due to this the current flow in one direction only.
Difference between AC and DC current.AC Current:
- It is a alternating current.
- It is bidirectional current.
- Power expenditure is low.
- It is suitable for long distance.
- It is generated from EMI.
- It is a direct current.
- It is unidirectional current.
- Power expenditure is high.
- It is not suitable for long distance.
- It is generated from battery.
- We receive the electric supply called Main supply or Mains.
- The two wires come in the house called L and N wire.
- The first wire is live wire (red colour).
- The second wire is neutral wire (black color).
- Another wire also comes in the house called Earth wire (green color).
- In our house, the potential difference comes is 220 volts.
- The wires are separated by circuit of 15 ampere current rating and other 5 ampere current rating for bulbs and fans etc.
- Appliances are connected in parallel to each other because of equal potential differences.
- The metallic body of appliances is connected with earth wire which provide a low resistance conducting path of current, thus it ensure that any leakage of current , the earth wire keep its potential to earth. It is known as Earthing.
- [ElECTRIC FUSE]=It prevent damage to the appliances and circuit due to overloading.
- [OVERLOADING]=overloading of an electric circuit mean when the current flow in a circuit it become more than the capacity of components in the circuit to regist the current. when too much current passes to electric circuit, overload occurs through electric wire which may cause wire to break.
- [SHORT-CIRCUIT]=Short circuit is an electrical circuit that allow a current to travel along and unintended path with very low electrical resistance. This result in an excessive current flowing through the circuit which may cause fire to break.
By -Yatendra Kumar
VECTORSTUDIES
