#### Magnetism and Magnetic Effects of Electric Current Book Back Questions

12th Standard EM

Reg.No. :
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Physics

Time : 00:45:00 Hrs
Total Marks : 30
5 x 1 = 5
1. Th e force experienced by a particle having mass m and charge q accelerated through a potential diff erence V when it is kept under perpendicular magnetic field $\vec { B }$ is

(a)

$\sqrt { \frac { 2{ q }^{ 3 }BV }{ m } }$

(b)

$\sqrt { \frac { { q }^{ 3 }{ B }^{ 2 }V }{ 2m } }$

(c)

$\sqrt { \frac { 2{ q }^{ 3 }{ B }^{ 2 }V }{ m } }$

(d)

$\sqrt { \frac { { 2q }^{ 3 }BV }{ { m }^{ 3 } } }$

2. Th ree wires of equal lengths are bent in the form of loops. One of the loops is circle, another is a semi-circle and the third one is a square. Th ey are placed in a uniform magnetic fi eld and same electric current is passed through them. Which of the following loop confi guration will experience greater torque ?

(a)

circle

(b)

semi-circle

(c)

square

(d)

all of them

3. A non-conducting charged ring of charge q, mass m and radius r is rotated with constant angular speed ω. Find the ratio of its magnetic moment with angular momentum is

(a)

$\\ \frac { q }{ m }$

(b)

$\\ \frac { 2q }{ m }$

(c)

$\\ \frac { q }{ 2m }$

(d)

$\\ \frac { q }{ 4m }$

4. The vertical component of Earth’s magnetic field at a place is equal to the horizontal component. What is the value of angle of dip at this place?

(a)

30°

(b)

45°

(c)

60°

(d)

90°

5. A simple pendulum with charged bob is oscillating with time period T and let θ be the angular displacement. If the uniform magnetic field i switched ON in a direction perpendicular to the plane of oscillation then

(a)

time period will decrease but θ will remain constant

(b)

time period remain constant but θ will decrease

(c)

both T and θ will remain the same

(d)

both T and θ will decrease

6. 3 x 2 = 6
7. State Ampere’s circuital law.

8. Compare dia, para and ferro-magnetism.

9. What is meant by hysteresis?

10. 3 x 3 = 9
11. The repulsive force between two magnetic poles in air is 9 x 10-3 N. If the two poles are equal in strength and are separated by a distance of 10 cm, calculate the pole strength of each pole.

12. Two materials X and Y are magnetised, whose intensity of magnetisation are 500
A m-1 and 2000 A m-1, respectively. If the magnetising field is 1000 A m-1, then which
one among these materials can be easily magnetized?.

13. Calculate the magnetic field at a point P which is perpendicular bisector to current carrying straight wire as shown in figure.

14. 2 x 5 = 10
15. Show that for a straight conductor, the magnetic field
$\overset { \rightarrow }{ B } =\frac { { \mu }_{ ° }I }{ 4\pi a } (cos\varphi _{ 1 }-cos\varphi _{ 2 })\hat { n }$
$=\frac { { \mu }_{ ° }I }{ 4\pi a } (sin{ \theta }_{ 1 }+sin{ \theta }_{ 2 })\hat { n }$

16. Let E be the electric field of magnitude 6.0 × 106 N C-1 and B be the magnetic field
magnitude 0.83 T. Suppose an electron is accelerated with a potential of 200 V, will
it show zero deflection?. If not, at what potential will it show zero deflection.