Electric current and magnetism
Electric current and magnetism
Q1. (A) Choose the correct option and rewrite the following.1. The device used for the current production is called ___________
A Voltmeter
B. Ammeter
C. Power gauge
D Generator
2. At the time of short circuit, current __________ in the circuit
A. increases
B. Decreases
C. Remains the same
D. Steps increase
3. The direction of the magnetic field around the current conductor carrying current is given by ____________
A. Right hand thumb rule
B. Fleming's left hand regime
C. Fleming's right hand regime
D. None of these.
(B) Say true or false. If incorrect, write the correct sentence.
1. The magnetic poles are present in pairs. answer:. truth
2. Magnetic field increases as we move away from a magnet.
answer:. False: - The magnetic field decreases because we move away from a magnet.
3. The magnetic lines of force always cross each other.
answer:. False: - Magnetic lines of force do not cross one another.
4. Electric Generator is used to generate current. answer:. truth
(C) Find odd one out
1. Loudspeaker, microphone, electric motor, bar magnet.
answer:. Bar Magnet: - It is a magnet while the other is the working device on electromagnetism.
2. Armature coils, brushes, communicators, direct current. answer:. Direct current: - The rest are the parts of the generator.
3. Fuse, insulating material, rubber boots, generator.
answer:. Generators: - There are safety measures in using the rest of the power.
4. Voltmeter, emitter, galvanometer, thermometer.
answer:. Thermometer: - The remaining electromagnetic dive working on.
Q2. Define
1. Magnetic field: - The area around the magnet, which has the power of attraction and replication, is called "magnetic field".
2. Solonoid: - A wire of several turns in insulated copper wire wrapped in the shape of the cylinder is called solonoid.
3. Electric Motor: - A device that converts electrical energy into mechanical energy is called electric motor.
Q3. State the rules
1. Fleming's Right Hand Rule
1) Stretch the thumb, forefinger
and middle finger of the right hand so that they are perpendicular to each
other
2) If the forefinger
indicates the direction of the magnetic field and the thumb shows the direction
of the motion of conductor, then the middle finger will show the direction of
induced current.
2. Fleming's left hand rule:
Ans. :- Stretch the forefinger, the central finger and the thumb of you left hand mutually perpendicular to each other. If the forefinger shows the direction of the field and the central finger shows the direction of the current, then the thumb will point towards the direction of the motion of the conductor.
3. Right hand thumb rule
Imagine that you are holding a current carrying straight conductor in your right hand such that the thumb points towards the direction current, then the curled fingers around the conductor will give the direction of the magnetic field. This is known as right hand thumb rule
Explain the construction, work and use of electric motors.
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| Electric motor |
1. Electric Motor
answer:. A device that converts electrical energy into mechanical energy is called electric motor.
Principle: - The electric motor works on the principle that the current conductor conductor kept in the magnetic field experiences the force.
Construction:
Electric motor
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| Construction of electric motor |
1) Armature coil: - A large number of insulated copper wire wounds at the core of iron in rectangular shape forms an armature coil ABCD shown in the above figure.
2) Strong Magnet: - The armature coil is placed between two pole pieces (N and S) of a strong magnet. It provides a strong magnetic field.
3) Split Ring Commutator: - There are two parts of the metal ring (R1 and R2) in it. The ends of the armature coil are connected to these rings. The commutator reverses the current direction in the armature coil.
4) Brush: - Two carbon brushes are used to press B1 and B2, the commutator.
5) Battery: - The battery supplies the current (D.C.) to the armature coil
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| Motor |
Working: -
1) When current is passed through the coil ABCD,
arms AB and CD experience force. According to Fleming's left hand rule the
force experienced by arm AB is in the downward direction and arm CD in the
upward direction
2) Both these forces are equal
and opposite. This force rotates the coil in clockwise direction until the coil
is vertical.
4) But the coil does not stop due to inertia. It goes on rotating until the commutator again comes in contact with the brushes B1 and B2
5) Again the current starts passing through coil and the arm AB rotates through 900, 1800, 2700 and 3600. Now the force acting on arm AB is downward and CD is upward. Again this force moves the coil in clockwise direction
6) Thus, the coil rotates with the help of electrical energy. The coil of DC motor continues to rotate in the same direction
Uses of DC motor:
1) These motors are used in home appliances such as mixers, blender, refrigerators and washing machines.
2) These motors are used in electric fans, hair dryer, record player, tape recorder and flyers.
3) These motors are used in electric cars, rolling mills, electric cranes, electric lift and electric trains.
An electric appliance that converts mechanical energy into electrical energy is called an electrical generator.
Principle: Electrical generator works on the principle of electromagnetic induction. When the electric generator coil rotates in the magnetic field, the magnetic field induces a flow in this string. This induced flux then flows into the circuit connected to the coil.
Types of electric generators:
1. AC Generator
2. DC Generator
The main components of the AC generator are shown in Figures.
1. Armature 2. Strong magnet 3. Slip rings and 4. Brush.
Armature, strong magnet and brush are the same for electric motor
slip rings:-
The two ends of the armature coil are connected to two bronze slip rings R1 and R2. These rings revolve with armature coils.
A. When the armature coil ABCD rotates in a magnetic field provided by strong magnets, it cuts down the force's magnetic lines.
B. Thus, the changing magnetic field produces induced flux in the wire. The direction of the induced flow is determined by the rules of Fleming's right hand.
C. Currently, through the brush B1, in the first part of the revolution there is a revolution in opposite direction and in the next half revolution through the revolutionary B2, this process is repeated.
D. Therefore, the produced induced current nature is optional. Such a current is known as alternate flow.
2. DC Generator:
A generator which converts mechanical energy into electrical energy in the form of direct current is called a DC generator.
Construction:-
The main components of the DC generator are:
1. Armature Coil 2. Strong Magnets 3. Split Rings or Commutator 4. Brush 5. Bulb.
Components like armature coils, strong magnet, brushes are used for AC generators. Slip rings or communicators are similar to use in electric motor.
Working of DC Generator:
(A) When the DC generator coil rotates in the magnetic field, then there is a possible difference in the coil. It gives rise to current flow of flow. It is shown by the glow of the bulb.
(B) In the DC generator, the flow of current in the circuit is in the same direction as long as the wire rotates in the magnetic field.
(C) This is because a brush is always exposed to the arm to move towards the armature and the other is in contact with the arm's arm towards the bottom in the magnetic field.
1. If the current in coil A is changed, then some current will be induced in coil B.
2. As the current in coil A changes, the magnetic field related to it also change
3. Due to the changing magnetic field, the current is induced in coil B.
2. Electric Generator.
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| Electric Generator |
Principle: Electrical generator works on the principle of electromagnetic induction. When the electric generator coil rotates in the magnetic field, the magnetic field induces a flow in this string. This induced flux then flows into the circuit connected to the coil.
Types of electric generators:
1. AC Generator
2. DC Generator
1. AC Generator: A generator which converts mechanical energy into electric energy in the form of alternating current is called AC Generator.
Construction:-
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| AC Generator |
The main components of the AC generator are shown in Figures.
1. Armature 2. Strong magnet 3. Slip rings and 4. Brush.
Armature, strong magnet and brush are the same for electric motor
slip rings:-
The two ends of the armature coil are connected to two bronze slip rings R1 and R2. These rings revolve with armature coils.
Working:
A. When the armature coil ABCD rotates in a magnetic field provided by strong magnets, it cuts down the force's magnetic lines.
B. Thus, the changing magnetic field produces induced flux in the wire. The direction of the induced flow is determined by the rules of Fleming's right hand.
C. Currently, through the brush B1, in the first part of the revolution there is a revolution in opposite direction and in the next half revolution through the revolutionary B2, this process is repeated.
D. Therefore, the produced induced current nature is optional. Such a current is known as alternate flow.
2. DC Generator:
A generator which converts mechanical energy into electrical energy in the form of direct current is called a DC generator.
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| DC Generator |
Construction:-
The main components of the DC generator are:
1. Armature Coil 2. Strong Magnets 3. Split Rings or Commutator 4. Brush 5. Bulb.
Components like armature coils, strong magnet, brushes are used for AC generators. Slip rings or communicators are similar to use in electric motor.
Working of DC Generator:
(A) When the DC generator coil rotates in the magnetic field, then there is a possible difference in the coil. It gives rise to current flow of flow. It is shown by the glow of the bulb.
(B) In the DC generator, the flow of current in the circuit is in the same direction as long as the wire rotates in the magnetic field.
(C) This is because a brush is always exposed to the arm to move towards the armature and the other is in contact with the arm's arm towards the bottom in the magnetic field.
Observe the figures. If current is changed in coil A, then will some current be stimulated in coil B? tell about.
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| Coil A & B |
1. If the current in coil A is changed, then some current will be induced in coil B.
2. As the current in coil A changes, the magnetic field related to it also change
3. Due to the changing magnetic field, the current is induced in coil B.
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