Changes

* clock and stopwatch

* clock and stopwatch

===Measuring DC amps===

===Ampere's Law===

Unlike the current transformer (previously) which can only sense AC amps, the Hall Effect sensor can also sense DC amps. It does this by measuring the magnetic field that a current creates.

Unlike the current transformer (previously) which can only sense AC amps, the Hall Effect sensor can also sense DC amps. It does this by measuring the magnetic field that a current creates.

*B in tesla (1 gauss = 10^-4 tesla)

*B in tesla (1 gauss = 10^-4 tesla)

*l in metres

*l in metres

*i in amps

*I in amps

and in the special case of the magnetic field B at a radius r from a wire in free space, the left side integral evaluates to B2πr and at a radius if 2.5mm from a wire carrying 1.5 amps , the field is (4π10^-7x1.5)/(2πx2.5x10^-3) = 1.2x10^-4 tesla or 1.2 gauss, at 1.3mV/gauss, the expected voltage is 1.56mV and the measured approximately 1.5 mV.

In the special case of a wire in free space, the integral is easy to evaluate. At a radius r, the field is uniform over a circular path round the wire , the path length is 2πr. So for the magnetic field B at a radius r from a wire in free space, B2πr=u0I.

 

 

This can be experimentally verified. At a radius of 2.5mm from a wire carrying 1.5 amps , the field is (4π10^-7x1.5)/(2πx2.5x10^-3) = 1.2x10^-4 tesla or 1.2 gauss, at 1.3mV/gauss, the expected voltage is 1.56mV and the measured approximately 1.5 mV.

[[File:Ampere-spacing.jpg]]

[[File:Ampere-spacing.jpg]]

 

Though useful for testing Amperes law, the above is too insensitive for most current measurement.

Though useful for testing Amperes law, the above is too insensitive for most current measurement.