Moving Charges and Magnetism Test

Result

Moving Charges and Magnetism Test - 80

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Weekly Quiz Competition

Question 1
1 / -0

Two long thin parallel conductors of the shape shown in figure carry direct currents $$ I_1 and I_2 $$ The separation between the conductors is a, the width of the right-hand conductor is equal to b. With both connductors lying in one plane, find the magnetic interaction force between them (per unit length)

A
$$ \frac { \mu _{ 0 } }{ 4\pi } \left( \frac { { 2I }_{ 1 }{ I }_{ 2 } }{ B } \right) ln\left( I+\frac { b }{ a } \right) $$

B
$$ \frac { \mu _{ 0 } }{ 4\pi } \left( \frac { { I }_{ 1 }{ I }_{ 2 } }{ B } \right) ln\left( I+\frac { b }{ a } \right) $$

C
$$ \frac { \mu _{ 0 } }{ \pi } \left( \frac { { I }_{ 1 }{ I }_{ 2 } }{ B } \right) ln\left( I+\frac { b }{ a } \right) $$

D
none

Solution
Question 2
1 / -0

Two parallel wires $$10cm$$ apart carry currents $$8A$$ in opposite direction. The magnetic field halfway between them will be

A
$$3.2 \times {10^{ - 5}}T$$

B
$$6.4 \times {10^{ - 5}}T$$

C
$$3.8 \times {10^{ - 5}}T$$

D
$$4.8 \times {10^{ - 5}}T$$
Question 3
1 / -0

A positive charge $$q$$ is projected in magnetic field of width $$\cfrac{mv}{\sqrt{2}qB}$$ with velocity $$v$$ as shown in figure. Then time taken by charged particle to emerge from the magnetic field is

A
$$\cfrac{m}{\sqrt{2}qB}$$

B
$$\cfrac{\pi m}{4qB}$$

C
$$\cfrac{\pi m}{2qB}$$

D
$$\cfrac{\pi m}{\sqrt{2}qB}$$

Solution
Question 4
1 / -0

Two parallel straight wires carry current $$I_1$$ and $$I_2$$ as shown below. The points where net magnetic field will be always outside the plane of paper lies in

A
Region I

B
Region II

C
Region III

D
zero in all region
Question 5
1 / -0

Two parallel long wires of the length $$ 100 m $$ each are separated by a distance of $$ 40 cm $$ from each other. the current in each of them is $$ 200 A$$. The current flows in the same direction. The force acting between the two wires is :-

A
$$ 2 N $$ repulsive

B
$$ 2 N $$ attractive

C
$$ 0.2 N $$ repulsive

D
$$ 0.02 N $$ attractive

Solution
Question 6
1 / -0

A conducting wire of length $$'\iota '$$ is placed on a rough horizontal suriace, wncec a uniform horizontal magnetic field B perpendicular to the length of the wire exists. Least values of the horizontal forces required to move the rod when a current 'I' is established in the rod are observed to be $${ F }_{ 1 }\& { F }_{ 2 }(<{ F }_{ 1 })$$ for the two possible directions of the current through the rod respectively. What is the coefficient of friction between the rod and the surface?

A
$$\mu =\dfrac { { F }_{ 1 }-{ F }_{ 2 } }{ BIl } $$

B
$$\mu =\dfrac { { F }_{ 1 }+{ F }_{ 2 } }{ BIl } $$

C
$$\mu =\dfrac { { F }_{ 1 }+{ F }_{ 2 } }{ 2BIl } $$

D
$$\mu =\dfrac { { F }_{ 1 }-{ F }_{ 2 } }{ 2BIl } $$

Solution
Question 7
1 / -0

A negatively charged particle having magnitude of charge $$q=0.1c$$ and mass $$m=200gm$$ moves with speed $$v=10m/s$$ enters a region having magnetic field $$B=4T$$ making an angle $${60}^{o}$$ with X axis as shown if figure. The direction of magnetic field is out of the X-Y plane. A convex lens is placed at a distance $$14.3m$$ from origin. Region of magnetic field starts from origin and extends till lens. Focal length of lens is $$50cm$$.
Take X-axis as principle axis
Find the minimum value of initial velocity of change so that the image formed is virtual

A
$$7.2m/s$$

B
$$14.8m/s$$

C
$$16.4m/s$$

D
$$20m/s$$
Question 8
1 / -0

Consider a long, straight wire of cross-sectional area $$A$$ carrying a current $$i$$. Let there be $$n$$ free electrons per unit volume. An observer places himself on a trolley moving in the direction opposite to the current with a speed $$v = \dfrac { i } { n A e }$$ and separated from the wire by a distance $$r$$.The magnetic field seen by the observer is very nearly

A
$$\dfrac { \mu _ { 0 } i } { 2 \pi r }$$

B
zero

C
$$\dfrac { \mu _ { 0 } i } { \pi r }$$

D
$$\dfrac { 2 \mu _ { 0 } i } { \pi r }$$

Solution
Question 9
1 / -0

Suppose an isolated north pole is kept at the centre of a circular loop carrying a electric current i. The magnetic field due to the north pole at a point on the periphery of the wire is B. The radius of the loop is a. The force on the wire is :-

A
Nearly $$2\pi aiB$$ perpendicular to the plane of the wire

B
$$2\pi aiB$$ into the plane of the wire

C
$$\pi aiB$$ along the axis of the wire

D
zero

Solution
Question 10
1 / -0

A particle enters the region of a uniform magnetic field as shown in figure. The path of the particle inside the field is shown by a dark line. The particle is:

A
electrically neutral

B
positively charged

C
negatively charged

D
nothing definite can be said about the nature of the charge as the information given is inadequate

Solution