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Magnetic Field Strength Around a Wire

Magnetic Field Strength Around a Wire. From the demonstration, we saw that:. the magnetic field strength varies directly with the amount of current flowing through the wire i.e. B  I the magnetic field strength varies inversely with the distance from the wire. i.e.

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Magnetic Field Strength Around a Wire

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  1. Magnetic Field Strength Around a Wire

  2. From the demonstration, we saw that: • the magnetic field strength varies directly with the amount of current flowing through the wire • i.e. B  I • the magnetic field strength varies inversely with the distance from the wire. • i.e.

  3. Thus we combine these together to get • as an equation • for mathematical & historical reasons the constant k has been written as

  4. however we shall for simplicity use "k“ • Our formula then is • where B = magnetic field strength (Tesla) • I = current (Amps) • r = distance from wire (m) • k = permeability of free space constant = 2 x 10 -7

  5. Sample: A vertical wire carries a current of 25.0 A. What is the magnetic field strength 15 cm from the wire?

  6. Magnetic Field Strength inside a Loop • We predict the field strength will be greater inside a loop. There are wires all around the region exerting a magnetic field. The lines of flux reinforce each other. The formula for a single loop is r = radius of coil

  7. For a coil, the strength depends on the number of coils. (N)

  8. Sample: If the magnetic field strength at the centre of a loop of 12 coils is 4.00 x 10-4 T, and the radius is 12.0 cm, find the current that is flowing,

  9. Magnetic Field Strength inside a Solenoid • The formula for magnetic field strength inside a solenoid is • B = 2knI where n = number of turns / m

  10. Sample: A 10 cm long solenoid has 400 turns of wire and carries a current of 2.00 A. Calculate the magnetic field strength inside the solenoid. n = 400 turns / 0.1m = 4000 / m B = 2knI B = 22 x 10-7(4000)(2) B=1.0 x 10-2 T

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