Free Printable Target Physics [XII DPP-17] MAGNETIC EFFECT OF CURRENT

1.

Current flows due north in a horizontal transmission

line. Magnetic field at a point P vertically above it

directed

a)

North wards

b)

South wards

c)

Toward east

d)

Towards west

2.

Magnetic field due to a current carrying loop or a coil at
a distant axial point P is $B_1$ and at an equal distance in
it’s plane is $B_2$ then $\frac{B_1}{B_2}$ is

a)

2

b)

1

c)

$\frac{1}{2}$

d)

None of these

3.

Find the position of point from wire ‘B’ where net

magnetic field is zero due to following current

distribution

a)

4 cm

b)

\frac{30}{7}cm

c)

$\frac{12}{7}cm$

d)

2 cm

4.

Find out the magnitude of the magnetic field at point P

due to following current distribution

a)

$\frac{\mu_0ia}{\pi r^2}$

b)

$\frac{\mu_0ia^2}{\pi r}$

c)

$\frac{\mu_0ia}{2\pi r^2}$

d)

$\frac{2\mu_0ia}{\pi r^2}$

5.

What will be the resultant magnetic field at origin due

to four infinite length wires. If each wire produces

magnetic field ‘B’ at origin

a)

4 B

b)

$\sqrt{2}B$

c)

$2\sqrt{2}B$

d)

Zero

6.

Two parallel, long wires carry currents i₁and i₂with

i₁ > i₂ . When the currents are in the same direction,

the magnetic field at a point midway between the wires

is 10 µT. If the direction of is reversed, the field becomes

30 µT. The ratio i₁ / i₂ is

a)

4

b)

3

c)

2

d)

1

7.

A wire of fixed length is turned to form a coil of one turn.

It is again turned to form a coil of three turns. If in both

cases same amount of current is passed, then the ratio

of the intensities of magnetic field produced at the centre

of a coil will be

a)

9 times of first case

b)

$\frac{1}{9}$ times of first case

c)

3 times of first case

d)

$\frac{1}{3}$ times of first case

8.

A wire in the form of a square of side a carries a current
i. Then the magnetic induction at the centre of the
square wire is (Magnetic permeability of free space =
$\mu_0$ )

a)

$\frac{\mu_0i}{2\pi a}$

b)

$\frac{\mu_0i\sqrt{2}}{\pi a}$

c)

$\frac{2\sqrt{2}\mu_0i}{\pi a}$

d)

$\frac{\mu_0i}{\sqrt{2}\pi a}$

9.

The ratio of the magnetic field at the centre of a current

carrying circular wire and the magnetic field at the centre

of a square coil made from the same length of wire will

be

a)

$\frac{\pi^2}{4\sqrt{2}}$

b)

$\frac{\pi^2}{8\sqrt{2}}$

c)

$\frac{\pi}{2\sqrt{2}}$

d)

$\frac{\pi}{4\sqrt{2}}$

10.

The field B at the centre of a circular coil of radius r is

π times that due to a long straight wire at a distance r

from it, for equal currents here shows three cases; in

all cases the circular part has radius r and straight ones

are infinitely long. For same current the field B is the

centre P in cases 1, 2, 3 has the ratio

a)

$\left(-\frac{\pi}{2}\right):\left(\frac{\pi}{2}\right):\left(\frac{3\pi}{4}-\frac{1}{2}\right)$

b)

$\left(-\frac{\pi}{2}+1\right):\left(\frac{\pi}{2}+1\right):\left(\frac{3\pi}{4}+\frac{1}{2}\right)$

c)

$-\frac{\pi}{2}:\frac{\pi}{2}:\frac{3\pi}{4}$

d)

$\left(-\frac{\pi}{2}-1\right):\left(\frac{\pi}{2}-\frac{1}{2}\right):\left(\frac{3\pi}{4}+\frac{1}{2}\right)$

11.

Two infinite length wires carries currents 8A and 6A

respectively and placed along X and Y-axis. Magnetic

field at a point P (0, 0, d)m will be

a)

$\frac{7\mu_0}{\pi d}$

b)

$\frac{10\mu_0}{\pi d}$

c)

$\frac{14\mu_0}{\pi d}$

d)

$\frac{5\mu_0}{\pi d}$

12.

An equilateral triangle of side ‘a’ carries a current i then find out the magnetic field at point P which is vertex of triangle

a)

$\frac{\mu_0i}{2\sqrt{3}\pi a}$ ⊗

b)

$\frac{\mu_0i}{2\sqrt{3}\pi a}$ ⊙

c)

$\frac{2\sqrt{3}\mu_0i}{\pi a}$ ⊙

d)

Zero

13.

A battery is connected between two points A and B on
the circumference of a uniform conducting ring of radius
r and resistance R. One of the arcs AB of the ring
subtends an angle $\theta$ at the centre. The value of, the
magnetic induction at the centre due to the current in
the ring is

a)

Proportional to 2 $\left(180^o-\theta\right)$

b)

Inversely proportional to r

c)

Zero, only if $\theta$ = $180^o$

d)

Zero for all values of $\theta$

14.

The earth’s magnetic induction at a certain point is
$7\times10^{-5}\ \frac{Wb}{m^2}$ . This is to be annulled by the magnetic
induction at the centre of a circular conducting loop of
radius 5 cm. The required current in the loop is

a)

0.56 A

b)

5.6 A

c)

0.28 A

d)

2.8 A

15.

A particle carrying a charge equal to 100 times the
charge on an electron is rotating per second in a circular
path of radius 0.8 metre. The value of the magnetic field
produced at the centre will be ( $\mu_0$ permeability for
vacuum)

a)

$\frac{10^{-7}}{\mu_0}$

b)

$10^{-17}\mu_0$

c)

$10^{-6}\mu_0$

d)

$10^{-7}\mu_0$

16.

Ratio of magnetic field at the centre of a current carrying coil of radius R and at a distance of 3R on its axis is

a)

$10\sqrt{10}$

b)

$20\sqrt{10}$

c)

$2\sqrt{10}$

d)

$\sqrt{10}$

17.

A circular current carrying coil has a radius R. The
distance from the centre of the coil on the axis where the magnetic induction will be $\frac{1}{8}$ th to its value at the centre of the coil, is

a)

$\frac{R}{\sqrt{3}}$

b)

$R\sqrt{3}$

c)

$2\sqrt{3R}$

d)

$\frac{2}{\sqrt{3}}R$

18.

An infinitely long conductor PQR is bent to form a right angle as shown. A current I flows through PQR. The magnetic field due to this current at the point M is $H_1$ . Now, another infinitely long straight conductor QS is connected at Q so that the current is $\frac{1}{2}$ in QR as well as in QS, the current in PQ remaining unchanged. The magnetic field at M is now $H_2$ . The ratio $\frac{H_1}{H_2}$ is given by

a)

$\frac{1}{2}$

b)

1

c)

$\frac{2}{3}$

d)

2

19.

Figure shows a square loop ABCD with edge length a. The resistance of the wire ABC is r and that of ADC is 2r. The value of magnetic field at the centre of the loop assuming uniform wire is

a)

$\frac{\sqrt{2}\mu_0i}{3\pi a}⊙$

b)

$\frac{\sqrt{2}\mu_0i}{3\pi a}⊗$

c)

$\frac{\sqrt{2}\mu_0i}{\pi a}⊙$

d)

$\frac{\sqrt{2}\mu_0i}{\pi a}⊗$

20.

A long solenoid has 200 turns per cm and carries a
current of 2.5 A. The magnetic field at its centre is $\left[\mu_0=4\pi\ 10^{-7\ }\frac{Wb}{m^2}\ \right]$

a)

$3.14\times\ 10^{-2\ }\frac{Wb}{m^2}$

b)

$6.28\times\ 10^{-2\ }\frac{Wb}{m^2}$

c)

$9.42\times\ 10^{-2\ }\frac{Wb}{m^2}$

d)

$12.56\times\ 10^{-2\ }\frac{Wb}{m^2}$

21.

A long solenoid is formed by winding 20 turns/cm. The
current necessary to produce a magnetic field of 20
millitesla inside the solenoid will be approximately $\left(\frac{\mu_0}{4\pi}=10^{-7}\ Tesla-\frac{metre}{ampre}\right)$

a)

8.0 A

b)

4.0 A

c)

2. A

d)

1.0 A

22.

Two solenoids having lengths L and 2L and the number

of loops N and 4N, both have the same current, then

the ratio of the magnetic field will be

a)

1 :2

b)

2 : 1

c)

1 : 4

d)

4 : 1

23.

The average radius of a toroid made on a ring of nonmagnetic material is 0.1 m and it has 500 turns. If it

carries 0.5 ampere current, then the magnetic field

produced along its circular axis inside the toroid will be

a)

$25\times10^{-2}Tesla$

b)

$5\times10^{-2}Tesla$

c)

$25\times10^{-4}Tesla$

d)

$5\times10^{-4}Tesla$

24.

For the solenoid shown in figure. The magnetic field at

point P is

a)

\frac{\mu_0ni}{4}\left(\sqrt{3}+1\right)

b)

$\frac{\sqrt{3}\mu_0ni}{4}$

c)

$\frac{\mu_0ni}{2}\left(\sqrt{3}+1\right)$

d)

$\frac{\mu_0ni}{4}\left(\sqrt{3}-1\right)$

25.

Figure shows the cress sectional view of the hollow
cylindrical conductor with inner radius ‘R’ and outer
radius ‘2R’, cylinder carrying uniformly distributed
current along it’s axis. The magnetic induction at point
‘P’ at a distance $\frac{3R}{2}$ from the axis of the cylinder will be

a)

Zero

b)

$\frac{5\mu_0i}{72\pi R}$

c)

$\frac{7\mu_0i}{18\pi R}$

d)

$\frac{5\mu_0i}{36\pi R}$

26.

Find magnetic field at centre O in each of the following
figure

a)

$\frac{\mu_0i}{r}⊗$

b)

$\frac{\mu_0i}{2r}⊙$

c)

$\frac{\mu_0i}{4r}⊗$

d)

$\frac{\mu_0i}{4r}⊙$

27.

Find magnetic field at centre O in each of the following
figure

a)

$\frac{\mu_0i}{4}\ \left(\frac{1}{r_1}-\frac{1}{r_2}\right)⊗$

b)

$\frac{\mu_0i}{4}\ \left(\frac{1}{r_1}+\frac{1}{r_2}\right)⊗$

c)

$\frac{\mu_0i}{4}\ \left(\frac{1}{r_1}-\frac{1}{r_2}\right)⊙$

d)

Zero

28.

Find magnetic field at centre O in each of the following
figure

a)

$\frac{\mu_0i}{4}\ \left(\frac{1}{r_1}-\frac{1}{r_2}\right)⊗$

b)

$\frac{\mu_0i}{4}\ \left(\frac{1}{r_1}+\frac{1}{r_2}\right)⊗$

c)

$\frac{\mu_0i}{4}\ \left(\frac{1}{r_1}-\frac{1}{r_2}\right)⊙$

d)

Zero

29.

Find magnetic field at centre O in each of each of the
following figure

a)

$\frac{\mu_0i}{2r}⊙$

b)

$\frac{\mu_0i}{2r}⊗$

c)

$\frac{3\mu_0i}{8r}⊗$

d)

$\frac{3\mu_0i}{8r}⊙$

30.

Find magnetic field at centre O in each of each of the

following figure

a)

$\frac{\mu_0}{2\pi}\ \frac{i}{r}\left(\pi-2\right)⊗$

b)

$\frac{\mu_{0i}}{2}.\ \frac{i}{r}\left(\pi+2\right)⊙$

c)

$\frac{\mu_0i}{4r}⊗$

d)

$\frac{\mu_0i}{4r}⊙$

31.

Find magnetic field at centre O in each of each of the

following figure

a)

\frac{\mu_0}{2r}\ \frac{2i}{r}\left(\pi+1\right)\ ⊗

b)

$\frac{\mu_0}{2r}\ \frac{2i}{r}\left(\pi-1\right)\ ⊗$

c)

Zero

d)

Infinite

Target Physics [XII DPP-17] MAGNETIC EFFECT OF CURRENT

Total questions: 31

Worksheet time: 2hrs 33mins

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