|

Engineering Competition Physics Questions

Blazing goIITian

Posted on
24 Oct 2009 15:37:42 IST
Posts: 615
24 Oct 2009 15:37:42 IST
0 people liked this
18
2479
Engineering Competition Physics Questions
Engineering Entrance , JEE Main , JEE Main & Advanced , Physics , Electromagnetism , academic
electromagnetic Induction:

The Production of Electromotive force in a conductor when
there is a change in the magnetic flux linkage with coil or
when there is a relative motion of the conductor across a
magnetic field.

Magnetic Flux:

Magnetic Flux through an area dS in a magnetic Field B is

=  B.dS

When the Flux of a magnetic field through a loop changes,
an emf is induced in the loop which is given by :

= -d/dt

Where

=  B.dS is the Flux through the loop.

The EmF lasts as long as the magnetic Field changes.

Lenz's Law:

It states that the polarity of the induced Emf and the
direction of the induced current is such tat it opposes the

change that has induced it.

Motional Emf:

When a conducting rod of length L moves with a velocity V
in a magnetic field B such that B,V & L are mutually per-
-pendicular to each other then the induced Emf is :

= BLV

This is called as motional Emf.If the circuit is completed
the direction of the current can be worked out by Lenz's
Law.

Induced Electric Field:

A time varying Magnetic field induces an electric field.If
a conductor is placed in this field , an induced Emf is
produced :

=  E.dL (Here  is Cyclic Integral)

= - d/dt

E.dL = - d/dt (Cyclic Integral)

Self Induction:

A Current Carying loop produces a magentic Flux Through
the area.

= Li Where L is the Self Inductance.

If Current Changes in the loop the Induced Emf is given
by:

= - d/dt = -L di/dt

For a Solenoid of n turns,

= -n d/dt  B.dS

Self Inductance of a long solenoid is:

L = r0n2LA

Where

r is the relative magnetic permeability of the core , n is
no. of turns per unit length , L is the length of  solenoid.

and A is the cross-sectional area of the solenoid.

Mutual Inductance:

A changing current in one circuit causes a changing Flux &
hence an induced Emf in a neighbouring circuit.

N22 = Mi1

Where M is the Mutual Inductance of coils 1  2

M = N22/i1 = N11/i2

1 = -M di1/dt

2 = -M di2/dt

Alternating Current and Voltage:

Current and Voltage varying Sinusoidally are called as AC
and AV (Alternating Current and Voltage)

V = V0Sint

i = i0Sint

Mean Values of Voltage and Current:

(a)In one complete cycle:

V = 0 , i = 0

(b)In Half Cycle:

V = 2V0/ , i = 2i0/

(c)Root mean square Values:

Vrms = V0/2

irms = i0/2

Where V0 and i0 are peak Voltage and current.

AC Circuit with a Resistor:

E = E0Sint = E0Sint/R

AC Circuit with a capacitor:

V = E0Sint

i = E0/(1/C) [ Sin(t+/2) ]

Xc = 1/C is capacitive Reactance.

i = i0Sin(t + /2)

AC Circuit with an inductor:

V = E0Sint

i = i0Sin(t - /2)  {Voltage Leading}

XL = L Inductive Reactance.

LCR Circuit (Inductor,capacitor,Resistor Circuit in series):

Impedance , Z =  (L - 1/C)2 + R2

The above Expressino can be very well be given as:

Z = (XL-XC)2 + R2 ,

For Phase angle

Tan = XL-XC/R

Resonance:

L = 1/C

The Impedance of the circuit is equal to R only.

0 = 1/LC

f0 = 1/2LC  (Resonance Frequency)

Power:

Average Power ,

Pavg = Erms.Irms.Cos

Pavg = 1/2*E0I0Cos

Where Cos is the power factor.

Cos = R/Z

Choke Coil:

A Coil with low resistance and high inductance used to reduce current in AC Circuit without much heat loss is
called as a Choke Coil.

Power factor , Cos = R / (L - 1/C)2 + R2

R is Low and L is High thus is Reducing current.

Hope you all find it useful.

I have typed this whole thing

plZ rate me if useful.

Cheers!!!!!!!!!!!!@@@@@@!!!!!!!!!!!

Forum Expert
Joined: 1 Jun 2009 13:31:11 IST
Posts: 2456
13 Nov 2009 13:11:38 IST
0 people liked this

nice post..............

Blazing goIITian

Joined: 11 Sep 2008 12:38:20 IST
Posts: 1159
13 Nov 2009 20:22:19 IST
0 people liked this

good contribution

Blazing goIITian

Joined: 25 Jul 2009 21:09:59 IST
Posts: 615
13 Nov 2009 20:23:14 IST
0 people liked this

Blazing goIITian

Joined: 8 Oct 2008 14:46:21 IST
Posts: 8064
13 Nov 2009 22:42:08 IST
0 people liked this

excellent dude

Hot goIITian

Joined: 1 Sep 2009 20:37:43 IST
Posts: 172
13 Nov 2009 22:43:44 IST
0 people liked this

thanx a lot......... xcellent job........

Cool goIITian

Joined: 26 Jun 2009 21:41:21 IST
Posts: 90
14 Nov 2009 22:14:43 IST
0 people liked this

THNXX ALOT 4 SUCH GREAT COLLECTION OF BRIEF NOTES>>>INVALUABLE MAN>>>THUMBX UP 4 AHEAD>>

Blazing goIITian

Joined: 25 Jul 2009 21:09:59 IST
Posts: 615
15 Nov 2009 09:30:16 IST
0 people liked this

Blazing goIITian

Joined: 9 May 2009 09:33:23 IST
Posts: 831
15 Nov 2009 10:13:12 IST
0 people liked this

yeah gud job dude ...5 more....

Hot goIITian

Joined: 2 Apr 2009 14:09:47 IST
Posts: 161
15 Nov 2009 21:08:54 IST
0 people liked this

nice one yaar.........

Blazing goIITian

Joined: 25 Jul 2009 21:09:59 IST
Posts: 615
16 Nov 2009 20:05:34 IST
0 people liked this

Blazing goIITian

Joined: 9 May 2009 21:08:29 IST
Posts: 766
17 Nov 2009 19:09:57 IST
0 people liked this

really a very good post dude!

New kid on the Block

Joined: 25 Jul 2008 19:51:41 IST
Posts: 2
18 Nov 2009 18:06:21 IST
0 people liked this

thanks a lot for the post........Its like the whole of magnetism covered in here!!!!

New kid on the Block

Joined: 25 Jul 2008 19:51:41 IST
Posts: 2
18 Nov 2009 18:06:48 IST
0 people liked this

sorry that was electromagnetism

Blazing goIITian

Joined: 25 Jul 2009 21:09:59 IST
Posts: 615
19 Nov 2009 19:01:14 IST
0 people liked this

thanks dude >>>>>>>>>>>>> but still i expect more comments !!

Cool goIITian

Joined: 22 Nov 2008 15:50:27 IST
Posts: 45
23 Nov 2009 18:19:56 IST
0 people liked this

gud job yaar...keep up the gud work

New kid on the Block

Joined: 24 Mar 2009 17:20:02 IST
Posts: 3
23 Nov 2009 20:01:00 IST
0 people liked this

THANKS A LOT YAAR VERY USEFUL..

New kid on the Block

Joined: 11 Sep 2011 16:51:10 IST
Posts: 1
11 Sep 2011 16:51:13 IST
0 people liked this

u did a fabulous job dude. thankx..............

Scorching goIITian

Joined: 1 Jun 2011 05:26:27 IST
Posts: 207
11 Sep 2011 17:30:45 IST
0 people liked this

Nice post dude ..Thankzz a lot brthr ;-)

 Some HTML allowed. Keep your comments above the belt or risk having them deleted. Signup for a avatar to have your pictures show up by your comment If Members see a thread that violates the Posting Rules, bring it to the attention of the Moderator Team

## For Quick Info

Name

Mobile

E-mail

City

Class

Vertical Limit

Top Contributors
All Time This Month Last Week
1. Bipin Dubey
 Altitude - 16545 m Post - 7958
2. Himanshu
 Altitude - 10925 m Post - 3836
3. Hari Shankar
 Altitude - 10085 m Post - 2217
4. edison
 Altitude - 10825 m Post - 7804
5. Sagar Saxena
 Altitude - 8635 m Post - 8064