CBSE Mgnetic Effect and Electric Subject Notes

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Mgnetic Effect and Electric

Mgnetic Effect and Electric

Factors affecting Magnetic field due to current in a solenoid

1. Magnetic field is directly proportional to the number of turns in the coil.
2. It is directly proportional to the current passing through it.
3. It is inversely proportional to the length of air gaps between the poles.
4. It depends on the nature of the core material used in the solenoid. Electromagnet.

An electromagnet consists of a long coil of insulated copper wire wrapped around a soft iron core. It is a temporary magnet as it works as long as current is passed through it. Factors affecting the strength of magnetic field of an electromagnet

The strength of magnetic field of an electromagnet is -

1. Directly proportional to the number of turns.
2. Directly proportional to the current flowing through it.
3. Inversely proportional to the length of air gaps between the poles.

Uses of electromagnet

1. They are used in electrical devices such as electric bell, electric fan, motor, and generator.
2. They are used for lifting and transporting large mass of iron.
3. They are used in medical practices for removing pieces of iron from wound and used in MRI.

Permanent magnets

A permanent magnet is made from steel alloys like carbon steel, chromium steel, cobalt steel, etc. They are weaker than electromagnets and their strength and polarity cannot be changed. Force on a current carrying conductor in a magnetic field.

A current carrying conductor placed in a magnetic field experi- ences a force due to the interaction between

1. Magnetic field due to current carrying conductor and
2. External magnetic field in which conductor is placed.

Force on a current carrying conductor in a magnetic field A current carrying conductor placed in a magnetic field experi- ences a force due to the interaction between

1. Magnetic field due to current carrying conductor and
2. External magnetic field in which conductor is placed.

Flemming's Left Hand Rule If we stretch our thumb, fore finger and the middle finger of our left hand mutually perpendicular and if the fore finger represents the direction of magnetic field and the middle finger represents the direction of current then the thumb represents the direction of motion in conductor.

Electric motor A motor is the device which converts electrical energy into mechanical energy. It has a shaft which rotates continuously when current is passed through it. It is used in electric fans, mixer grinder, etc.

Principle of electric motor When a rectangular coil of copper wire is placed in a magnetic field and current is passed through it, a force acts on the coil which rotates it continuously. Electromagnetic induction. The production of electric current by moving a straight conductor in a magnetic field is called electromagnetic induction. It is the production of electricity from magnetism.

Flemming's Right Hand Rule. If we stretch our thumb, fore finger and the middle finger of our right hand mutually perpendicular and if the fore finger represents the direction of magnetic field and the thumb represents the direction of motion in conductor then the middle finger represents the direction of induced current in the conductor.

Electric generator A generator is a machine which is used to generate electric current by converting mechanical energy into electrical energy. There are two types of generators - alternating current (AC) generator and direct current (DC) generator.

Principle of electric generator When a coil of copper wire is moved in a strong magnetic field, a current is induced in the coil.

Earthing The appliances that have metallic body (like electric iron, toaster, refrigerator, etc.) are connected with green wire which provides a low resistance conducting path for the current and keeps the body of appliance at the potential of the earth. This is called earthing. Earthing is done to save ourselves from electric shocks. Electric fuse The device having a short length of thin wire which is made of alloy lead and tin is called fuse wire or electric fuse. It has a very low melting point. It melts and breaks the circuit if the current exceeds the safe value. Fuse wire is connected in series in the circuit.