induksi elektromagnetik

Electromagnetic Induction

Induced electromotive force

If a coil or wire is moved in magnetic field, at the end of wire or coir will appear potential difference called induced electromotive force (induced EMF). The potential difference produced electric current in the wire or coil called induced current.

Inducced current is produced by difference potential called induced electromotive force (EMF). Induced EMF is can appear because of the presence of relative motion between the coil and bar magnet, induced EMF is one example of electromagnetic induction.

To increase induced EMF it can be done by the method of:

a.       Accelerating the motion of taking in and out a bar magnet.

b.      Adding the number of winding in the coil.

c.       Using a stronger magnet.

Generator

Generator is machine that change kinetic/mechanical energy into electric energy.

Principally, a generator consists of rectangle-shaped coil that is located in a strong enough magnetic field.this magnetic field stems from two magnetic field that flank a coil, so the magnetic force lines that go out from the north pole (N) willl penetrate the coil before reaching the south pole (S). when the coil is rotate, the number of magnetic force lines will change according to the position of the coil in relation to magnet. The change of magnetic force lines produced induced EMF at the end of the coil and finally produced elctric energy.

There are two kind of generator. Those are alternating current and direct current generator. The difference of those two kind is located in its conductor ring.

 

Transformator

In figure. A is connected to the sourece of AC and B is connected to galvanometer. Coil A is called primer coil, and B is called secondary coil.when electric current flow fromAC corrent source in primary coil. Around the coil magnetic force lines appear. Some of the magnetic force lines from the primary coil enter the secondary coil. Because the elctric current thet is produced by the AC current source is allternating current, the number of its magnetic force lines will change againts times. This cause the number of its magnetic force lines that are covered by the secondary coil will also change. As a result induced electric current will flow in the secondary coil and the galvanometer’s needle will deflected.

Working principle of transformator

If you observe a transformator, you will see the number of winding in both coil differenct. One winding is more then the other.

The difference of the number of winding in primary or secondary coils will determines the function of the transformator, whether to step up (increase) or step down (decrease) voltages.

The ratio between the number of winding in primary and secondary coils to the voltages in primary and secondary coils in a tranformer is formulated by:

Ry coils

Where:

Vs= voltage in primary coils

Vp= voltage in secondary coils

Ns= winding in secondry coils

Np= winding in primary coils

In an ideal transformator, power that runs from a primary coil to the secondary coil is equal to 100% (n=100%).

Pp=Ps

Vp Ip= Vs Is

=

Ip= electric current in primery coil

Is= electric current in secondary coil

The efficiency of transformator

=the efficiency of transformator (100%)

Comprehension test 6

1.       Scientist that observed the phenomenon of electromagnetic induction….

a.       Newton-faraday

b.      Einstein-Newton

c.       Edison-faraday

d.      Oersted-Faraday

2.       Generating electric current by moving a conductor passing through a magnetic field is called…

a.       Electromagnetic induction

b.      Electromagnetic force

c.       Magnet

d.      Ferromagnetic

3.       The current that is produced EMF is…

a.       Magnetic current

b.      Electric current

c.       Induced current

d.      All are correct

4.       Induced current that happens when a bar magnet is moved in and out of the coil is…current.

a.       AC

b.      DC

c.       Induced

d.      Eddy

5.       PLTA uses a machine to change mechanical energy to electric energy is…

a.       Turbine

b.      Magnet

c.       Generator

d.      EMF

6.       A bicycle eses a dynamo as a voltage source to turn on the lamp. If the bycicle is operate faster, the glow of lamp will…

a.       Go off

b.      Remain constant

c.       Be brighter

d.      Be dimmer

7.       A step up transformator function to…

a.       Increase electric current

b.      Increase electric voltage

c.       Change AC to DC

d.      Change DC to AC

8.       The number of winding in a transformator will be direcly proportional to…

a.       Current

b.      Power

c.       Voltage

d.      All are correct

9.       the ratio (Ns/Np) is….

a.       22/10

b.      10/22

c.       1/22

d.      22/1

10.   From no.9, if the winding in secondary coil is 20. In primary coil is…

a.       440

b.      220

c.       44

d.      22

11.   A step up transformator has primary windings of 1200 and secondary winding is 6000. If primary coil is connected to 110 V, the voltage in secondary coil is….

a.       220 V

b.      440 V

c.       550 V

d.      500 V

12.   The ratio of the number of primary and secondary winding is 2:5. If the secondary voltage is 120 V, the primary voltage is…

a.       12 V

b.      48 V

c.       40 V

d.      30 V

13.   The valid equation of transformator is…

a.       Ns/Np=Is/Np

b.      Vs/Vp=Is/Ip

c.       Ns/Np=Vs/Np

d.      Vs/Ns=Vp/Np

14.   The transformator of a radio decrease voltage from 220 V to 6V. if the secondary 24 windind an current of 6.1 A, the number of primary winding is…

a.       660

b.      550

c.       440

d.      880

15.   The primary voltage is 220 V, the primary current is 4A, and secondary current is 2 A. the secondary voltage is…V

a.       55

b.      110

c.       440

d.      880