chapter three self induction

Question 1

diff self inductiion

Answer 1

it is the electromagnetic effect in the same coil as E.M.F is induced when the intensity of the current increaeseor decreases in the same coil to resists the varition in the current intensity

Question 2

when the key is closed the cuurent wiil grow

what is the mean by grow

Answer 2

the current will grow [ take time to reach maximum value due to generation of opposing induced E.M.F by self induction

Question 3

when the key is opened the current will decay

what is mean by decay

Answer 3

the current will decay [take time to come to zero due to generation of forward induced E.M.F by self induction]

Question 4

expermen of self induction

Answer 4

1. To demonstrate the self induction of a coil
2. To verify lenz rule by using inductive coil

procedures

1. connect a strong electromagnetic coil [solenoid of large number of turns] in series with a battery 6 volt and a key
2. connect a neon lamp 180 volt in parallel with the coil

obsevation

• at the moment of switching on ;

the current will pass in the first turn to make it as shell magnet ( circulat coil ) produces ascending magnetic filed link with the following turns so opposing E.M.F will be induced oppeses the growth of the current

• at the moment of switching of ;

the current will decay so the magnetic filed link with following turns will decreases so Forward** E.M.F will be induced **oppeses the decay of the current

by increasing the number of turns of the coil , the induced E.M.F on switching off the circuit will be much large than that of the battery , this causes a neon lamp connected in parallel between the two terminals of the key glow which the E.M.F reaches up to 180 volt

NOTE ; An electric spark passes between the terminals of the key if there is neon lamp

Question 5

proof the relation on self induction

Answer 5

E_ind & Dø_m \ Dt

Dø_m \ Dt & DI \ Dt

E_ind = DI \ Dt

E_ind = constant x DI \ Dt

E_ind = – L x DI \ Dt

Question 6

the cofficient of selff induction of the coil OR self inductance

sympol and diff and relation and unit

Answer 6

1. L
2. it is the E.M.F induced in the coil when the current passing through the same coil changes by rate 1A\1sec
3. L = E_ind \ DI \ Dt
4. henary

Question 7

diff henary

Answer 7

it is the self inductance of a coil when E.M.F od 1 volt induced in the coil when the current passing through it change at a rate 1 A \ 1 sec

Question 8

the self inductance depends on

Answer 8

1. the number of vturns
2. the distance
3. the magnetic permeability of its core
4. the geometrical shape

Question 9

what is the application bassed on self induction

Answer 9

operating of the neon lamp

• magnetic energy is stored inside an inductive coil and then this energy will be discharge in evacuated tupe filled by an inert gas
• the atoms of the inert gas will be ionized and collide with the wall of the glass tupe wher is coverd by fluorescent material that glow when the inert gas ions collide with it

Question 10

induced E.M.FR will be produced in the coil by self induction in case of switching on or off the circuit GR

Answer 10

• in case of switching on , the current grows in the first turn so it acts as a shell magnet produces magnetic filled cut the other turns so opposite induced current will be generated to oppose growing the origanal current
• while in case of switching off , the current will decay and also its magnetic filled that link the turns of the coil wiil decay so forword current will be induced to resist the decreasing of the current

Question 11

induced E.M.F may not be produced ion the coil in case of swithcing on or of the circuit GR

Answer 11

if the coil douple wounded so the magnetic filef formed due to passing of the electric current in certain direction will be canceled due to magnetic filed formed due to passing of the electric current in the opposite direction

Question 12

self inductance of a cfoil increases when an iron core is used GR

Answer 12

becauce soft iron has iigh magnetic permaplity so it concentrates yhe magnetic flux lines which increases the magnetic denisty

Question 13

the self induction of va coil has no effect if its wires douple wounded

Answer 13

if the coil douple wounded so the magnetic filef formed due to passing of the electric current in certain direction will be canceled due to magnetic filed formed due to passing of the electric current in the opposite direction

Question 15

in standerd resistors are douple wounded in opposite direction GR

Answer 15

To avoid the self induction as the current will flow in two oppiste direction so the magnetic filed associated to the first will be cancled by the second

R=P x L\ A ⇒without additional self induction