3

CHAPTER

Measuring Devices

LETS LOOK AT THE INSTRUMENTS THAT ENGINEERS USE TO MEASURE ELECTRICAL QUANTITIES. Some measuring devices work because electric and magnetic fields produce forces proportional to the field intensity. Some meters determine electric current by measuring the amount of heat produced as charge carriers move through a medium with a known resistance. Some meters have small motors whose speed depends on the measured quantity of charge carriers. Still other meters count electrical pulses or cycles.

Electromagnetic Deflection

Early experimenters noticed that an electric current produces a magnetic field. They could detect this field by placing a magnetic compass near a wire. The compass pointed toward magnetic north when the ...

Get Teach Yourself Electricity and Electronics, Sixth Edition, 6th Edition now with O’Reilly online learning.

O’Reilly members experience live online training, plus books, videos, and digital content from 200+ publishers.