magnet1.pdf class 12 physics magnetic effects of current

Question practice physics magnet

1. ade

A current loop, having two circular arcs joined by two radial lines is shown in the
figure. It carries a current of 10 A. The magnetic field at point O will be close to:

x o 5 DJEE Main 2019]
@ 33.0 x 1077 o PASS + Gp

a 15 SLOT 7 he
a Le = Br su Rue Gi (e >
Os x 105 T mre £

7 | E 3)
O. x105T a ey
2

RAT KIO KO $ 3

1% Hoy \s
= ate Seyi i=10A
Vo E54 $ :

= lo3y 105

2. As shown in the figure, two infinitely long, identical wires are bent by 90° and placed
in such a way that the segments_LP and QM are along the x-axis, while segments PS

and QN are parallel to

the y-axis. If OP = OQ = 4 cm, and the magnitude of the

magnetic field at O is 10-* * T, and the two wires carry equal current (see figure), the
magnitude of the current in each wire and the direction of the magnetic field at O will

be (3, = 4 x 1077 NA*)

[JEE Main 2019]

Bp 1515
CRT
7 Sas
a3 f en Fe AY
9-47 5 uh
_y as Any | A
LE gr ANT
=

SRE

3. The magnetic field at the centre of current carrying circular loop is B. The magnetic
field at a distance of V3 times radius of the given circular loop from the center on its
axis is B,. The value of B,/B,, will be: [JEE Main 2022]

DIE
8%

4. i The magnetic field at the centre of a circular coil of radius r, due to current / flowing
through it, is B. The magnetic field at a point along the axis at a distance r/2 from the

centre is: EE Main 2022
Vaan oe D ]
Bae

© 2
o»
Re

e Se

Gj E,

Nat dy

5. © Match List-I with List-II:

@ ameawcsp1
@ 4.1, 8-11, c-1v/D-1
SS

A-III; B-I, C-IV, D-II

® A-II; B-I, C-IV, D-III

List] E List-II
(Current ee A field at point 0)

9. 6
Five parallel infinite wires are placed at the vertices of a regular polygon. Four wires
carry current J) each. While the fifth wire carries current 31, as shown. The resultant

magnetic field at the centre 0 is:

O o

Holo
2rra
an)
mn VE
Ta
0 = ULT
Ho7lo m

10. 2 A long straight wire, carrying current /, is bent at its midpoint to form an angle of 45°%
Magnetic field at point P, distance R from point of bendifig is equal to:

© (NZ = 1)uof
4TR

a (V2 + 1)01
4TR

@ (V2 + 1)u01
NT

(V2 = 1)uol
œ rm

11. 24 long infinite current carrying wire is bent in the shape as shown in figure. The
magnetic induction at point O is: a
Gate

+
Of Ngee A ee

Hol
27TR ©

Hol
TR ©

B MT :
LEO = y DASLUTS
[6) 2 na )

Hol

2mR

12. ° Match List-I with List-Il:

Codes:

P Q/R\/S

CSD SB ya VA:

A D B Cc

Dee An A
4) © DA B

A

a

A

D.

List-I
(Current configuration)

List-Il |
(Magnetic field at point

@

13. 10
A current carrying wire has the configuration as shown in the figure. Two semi-

infinite straight sections, each tangent to the same circle, are connected by a circular
arc, of angle 0 along the circumference of the circle, with all sections lying in the same
plane. What must be 6 in order for B(magnetic field) to be zero at the centre of the’

circle?

14. "In the loop shown, the magnetic induction at the point ‘0’ is

Hol (Ri — Ro
oom

15. 12
Two wires are wrapped over a wooden cylinder to form two coaxial loops carrying

currents i, and i,. If i, = 8i, the value of x for B = 0 at the origin O is:

:

17 — 1)R

pa _

San green
RAR) Rn R
CR MS

000
a

E

as

Rope ns re
Fe vor RE
2 Ries Bra

DR

16. >
A long straight wire along the z-axis carries a current / in the negative z direction. The

magnetic vector field B at a point having coordinates (x, y) in the z= 0 plane is:

PR DY CA

2n(x? + y2)

Hol GE ty
2 rata? Fo X

Hol ef = yi) te
3 Pata? Fy) B= ate 5)

(
a =

17. L

A long straight wire along the z-axis carries a current / in the negative z direction. The

magnetic vector field B at a point having coordinates

Hol (yt — xf)

a

Hol (xi + yf)
Hol (xf — yi)
2m(x? + y?)

Hol (xt — yf)
2m(x? + y?)

2n(x? + y?)

2n(x2 + y?)

y ene

Ar
21)

bi-

uy) in the z = 0 plane is:

18. Y
The magnetic field at point Pis

Hoi
4V2na

Hot
4V2ra 8,7
à par UE
Hot BA = aT ara

8V2na 2 oie 2
= 2 i x
ea eat

8/2na = wt OP 0, > - AS Ye X 21)
PE

aa YADA)

19. YA current carrying wire carries a current of 2A along the z-axis which is out of the
page while, another wire carrying current of 4A in the same direction lies parallel to
the first as shown in the figure. Then around which loop linking both wires SB. dl
will be zero?

A

3 #0- Goag= M|y-2-2]

A
3 (ams u) a None ofthese

20. 16
Rank the magnitude of value of f B. dl for the closed paths shown in figure from the

smallest to largest _

@ abcd,,
a ac

AS

«4 oe

21. TEE +

EA
A solenoid 50 cm long has 4 layers of winding of 350 turns each. If the current is 6A_

then magnetic field at the centre of solenoid is cine
— Naseem 2.
O 53» 10*7 NE 35 Á

a B- Hort
2.1x102T
Y zumot(l S2\ La ul |
3) 3.1x 10*T
a 41xX102T

22. (ri
Figure shows, in cross section, several conductors that carry currents through the
plane of figure. The currents have magnitude 1, = 4.0 A, I, = 2.0 A and J = 2.0 Ain
direction shown in figure. Find the value of line integral f B. dl along the given loop

@ =:1057m feu DE
lo)

@ 25<10<1m
=.)
Qo./

4 5 x 10-6Tm

23. 1
A current i flows through a closed loop as shown in the figure. If the part abc is a
circular arc of radius R and the part acis a straight wire, then the magnetic field at the

ere Mer
veo AE
Hot
@ 00-0

i
2 Hol or — 6+ tan 8)
TR

O Sa- 6 + tan 0)

B = ee]
= MT

EB un ee
— (nr — O + tan 0)

O= AT Jan

24. Cee
vi

Two coaxial circular loops 1 and 2, which form same semi vertical angle 6 at point O.
Same charges are uniformly distributed along. the circumference of both the loops.
The loops are rotating with same angular velocity in same direction about their axis
through centre of mass and perpendicular to their plane. If B, and B, are magnetic
field due to the loops 1 and 2 respectively, then

® Ba pe
ne Ba 2 Bm

Bj 1
Baz BAREMO

2 (arte

LE
I

25. 2\
In figure there are two concentric coils in perpendicular planes carrying equal
currents. Magnetic field at centre is B. If current in one coil becomes zero, then
magnitude of new magnetic field will be

B
© = Bro = ro. ds
ey
Y) eu

(pes
BV2 x

otk

26. 2
A long cylindrical conductor of radius R carries a current i as shown in figure. The
current density j is a function of distance from the axis (r) according gi = brlwhere b
>R

is a constant. Find an expression of the magnetic field B at a distance yy measured
from the axis Q
cr)

O Hobr? J1i=T (24100

3
di = by2av dy

Y
OE) np
o

27. The magnetic field at the point O in the given figure is

Hol
ee)
ol Ena (V3+ 1)

CEE yy

a zero

28. M
An electric current of / ampere is flowing in a long conductor as shown in figure. The
magnetic field at the centre of coil is AT ow
Fie ae

Hol 1
ry 2r (: 3 =)
Hol 1
Ee) =

Hol

Eù

if Zero

29. 2
Magnetic field induction at the centre of the regular hexagon coil in the given figure is
(every arm has resistance equal to R)

I
gi

4ur

I
= 8

Zero ve

tol
Anr

te ie

30. > et
Ampere circuital law is given by [ B.dl = Uplinsige for a closed loop. Now choose the

correct alternative

Magnetic field is due to all the current element inside as wally
outside the loop

Magnetic field is only due to the current element outside the as
Magnetic field is only due to the current element inside the loop X

Magnetic field is only due to the current element passing through
the loop

31. Fa coil having N turns is wound tightly in the form of a spiral with inner and outer
radii a and ru When a current / passes through the coil, the magnetic field
at the centre is

Ho NI pe oF td b-a emp Be N

@ 7 m of urna Pur unit leg > vi

(La)
2 2uoNI mat Hum im An tenga — bu
71
ann
2(b—a) "a d6= al

2x

bol” b de < AIN N HIN
Pe 2% (6-4) = ÊTE)
Á

32. =D. ij © ==

Fa current enters a uniform conducting loop of radius r at x and leaves at y. Calculate

the magnetic field at O due to the portion XAY of the loop
PAR Scan DE ee Fe etre)

Qe er
Hoißl2rr — 6) I
8mr zy (Para)

fs

1i0Qr — 6)
4m2r

Hoi
=— 9
Zr