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# Important Notes - Magnetic Effects of Electric Current - JEE Main

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### Important Notes - Magnetic Effects of Electric Current - JEE Main

1. 1. Magnetic effect of electric current
2. 2. Oersted’s Experiment 1. Every current carrying conductor has associated magnetic field and 2. Direction of the magnetic field at a point is perpendicular to a. Length of the conductor and
3. 3. b. The line joining the conductor and the given point. Features of Magnetic Field 1. Strength of the magnetic field at a point near a current carrying conductor is inversely proportional to the distance of the point from the conductor. 2. Strength of the magnetic field at a point near a current carrying conductor is directly proportional to the magnitude of current flowing through the conductor. 3. Direction of the magnetic field at a point near a current carrying conductor depends on the direction of the current flowing through the conductor. If the direction of the
4. 4. conductor is reversed, direction of the magnetic field reverses. Right Hand Rule „imagine the current carrying conductor to be held in your right hand, with the thumb outstretched and the fingers curled round it. In this situation, if the thumb indicates the
5. 5. direction of current, the curled fingers indicate the direction of the magnetic field around it.‟ Magnetic Induction The vector quantity used to describe the magnetic field is called magnetic induction (B). “Magnetic induction at a point is the magnetic flux density at that point.” Hence the unit of magnetic induction is 2 2 weber/m (Wb/m ).
6. 6. Biot Savart’s Law or Laplace’s Law The magnitude of magnetic induction at a point neat a current carrying conductor due to small element of the conductor of length dℓ carrying current I, at distance r from the element is directly proportional to a. current I flowing through the element
7. 7. b. length of the element dℓ c. sine of angle θ between the element and the line joining the midpoint of the element to the given point and inversely proportional to square of the distance between the midpoint of the element and the given point. The figure shows a conductor carrying current I. According to Biot - Savart‟s law the small magnetic induction dB a P is given as I d sin r2 dB 0 dB 4 Id sin r2 where 0 4 is a constant whose value is 10 In vector form dB 0 4 Id u r2 –7 Wb / Am
8. 8. According to right hand rule, the direction of dB is perpendicular to plane of paper directed inwards. For more information www.ednexa.com - Team Ednexa please visit