Calculating Fields near Wires and Solenoids
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Calculating Fields near Wires and Solenoids
You will already know that the magnetic field near a current gets weaker as you move further away from the current.
The magnetic field strength is inversely proportional to distance:
The magnetic field strength is proportional to current:
Combining these relationships gives:
where the constant depends on the shape of the conductor.
Field around a straight wire:
Where:
I = current throught the wire (A)
r = distance from the conductor (m)
Field in a long straight solenoid:
Where:
n = number of turns on the coil per metre (m-1)
I = current throught the solenoid (A)
The strength of a magnetic field can be found using a device called the Hall probe. It works on a principle based on the Hall effect.
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