Magnetic effect of current- part-III : Magnetic effect of current- part-III By R.Buvana
Magnetic devices : Magnetic devices The magnetic effect of electric current is generally used to detect and measure electric current and voltage. The measuring instruments are often called meters. The current detecting instrument is called galvanometer, the current measuring instrument is called ammeter, while voltage measuring instrument is called voltmeter.
Torque on a current carrying coil in a magnetic field : Torque on a current carrying coil in a magnetic field ?=nIBA cos?
?+a=90°
Cos?=Cos(90 ° - a)=Sin a
?=nIBASin a
?=nIA xB=M xB
Where M=magnetic dipole moment of the rectangular current loop. This torque tends to rotate the coil about its own axis. Its value changes with angle between plane of coil and direction of magnetic field.
Moving coil galvanometer : Moving coil galvanometer Moving coil galvanometer is an instrument used for detection and measurement of small electric currents.
Principle-Its working is based on the fact that when a current carrying coil is placed in a magnetic field, it experiences a torque.
?=nIBA(Sin a=1) ,?=k?
Conti… : Conti… Deflecting torque=restoring torque
nIBA=k?
I=k?/nBA
I=G? where G is galvanometer constant
Homework questions : Homework questions