Activities/Turtle Art/Using Turtle Art Sensors: Difference between revisions
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* clock and stopwatch | * clock and stopwatch | ||
=== | ===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. | ||
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*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 | ||
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]] | ||
===Measuring DC amps=== | |||
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. | ||