Moving Charges and Magnetism Test

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Moving Charges and Magnetism Test - 70

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Weekly Quiz Competition

Question 1
1 / -0

In case Hall effect for a strip having charge $$Q$$ and area of cross-section $$A$$, the Lorentz force is

A
Directly proportional to $$Q$$

B
Inversely proportional to $$Q$$

C
Inversely proportional to $$A$$

D
Directly proportional to $$A$$

Solution

$$\vec F = Q[\vec E + (\vec v \times \vec B)]$$
So, $$F \propto Q$$
Question 2
1 / -0

" On flowing current in a conducting wire the magnetic field produces around it". It is a law of

A
Lenz

B
Ampere

C
Ohm

D
Maxwell

Solution

The aboove statement is ampere's law.
Question 3
1 / -0

Mixed $$He^+$$ and $$O^{2+}$$ ions (mass of $$He^+=4$$ amu and that of $$O^{2+}=16$$ amu) beam passes a region of constant perpendicular magnetic field. If kinetic energy of all the ions is same then

A
$$He^+$$ ions will be deflected more than those of $$O^{2+}$$

B
$$He^+$$ ions will be deflected less than those of $$O^{2+}$$

C
All the ions will be deflected equally

D
No ions will be deflected

Solution

$$r=\dfrac {\sqrt {2mK}}{qB}\Rightarrow r\propto \dfrac {\sqrt m}{q}\Rightarrow \dfrac {r_{He^+}}{r_{O^{++}}}=\sqrt {\dfrac {m_{He^+}}{m_{O^{++}}}}\times \dfrac {q_{O^{++}}}{q_{He^+}}$$
$$=\sqrt {\dfrac {4}{16}}\times \dfrac {2}{1}=\dfrac {1}{1}$$. Then will deflect equality.
Question 4
1 / -0

If cathode rays are projected at right angles to a magnetic field, their trajectory is

A
Ellipse

B
Circle

C
Parabola

D
None of these

Solution

Let the magnetic field be along North direction. Let cathode ray pass perpendicular to the magnetic field towards east.then it gets deflected downwards.
Fleming's left hand rule is meant for the movement of positively charged particles. But cathode rays are stream of negatively charged electrons. So opposite to the previous one.
And like postive charge it will make a circular trajectory.
Question 5
1 / -0

A beam of electrons and protons move parallel to each other in the same direction, then they

A
Attract each other

B
repel each other

C
No relation

D
Neither attract nor repel

Solution

The flow of positive chage is taken as the direction of current.
So, here the currents are in opposite direction so, they will repel each other.
Question 6
1 / -0

Three long, straight parallel wires carrying current, are arranged as shown in figure. The force experienced by a $$25\ cm$$ length of wire $$C$$ is

A
$$10^{-3}\ N$$

B
$$2.5 \times \ 10^{-3}\ N$$

C
Zero

D
$$1.5 \times 10^{-3}\ N$$

Solution

Force on wire $$C$$ due to wire $$D$$
$$F_D=10^{-7} \times \dfrac{2 \times 30 \times 10}{2 \times 10^{-2}} \times 25 \times 10^{-2}=5 \times 10^{-4}\ N$$ (towards right)
Force on wire $$C$$ due to wire $$G$$

$$F_G=10^{-7} \times \dfrac{2 \times 20 \times 10}{2 \times 10^{-2}} \times 25 \times 10^{-2}=5 \times 10^{-4}\ N$$ (towards left)
$$\Rightarrow$$ Net force on wire $$C$$ is $$F_{net}=F_D- F_G=0$$
Question 7
1 / -0

An electron and a proton have equal kinetic energies. They enter in a magnetic perpendicular. They

A
Both will follow a circular path with same radius

B
Both will follow a helical path

C
Both will follow a parabolic path

D
All the statements ate false

Solution

Particles entering perpendicular, hence they will describe circular path. Since their masses are different so they will described path of difference radii.
Question 8
1 / -0

Assertion : An electron is not deflected on passing through certain region of space. This observation confirms that there is no magnetic field in that region.
Reason : The deflection of electron depends on angle between velocity of electron and direction of magnetic field.

A
If both assertion and reason are true and the reason is the correct explanation of the assertion.

B
If both assertion and reason are true but reason is not the correct explanation of the assertion.

C
If assertion is true but reason is false.

D
If the assertion and reason both are false.

E
Iassertion is false but reason is true.

Solution

If electrons is moving parallel to the magnetic field, then the electron is not deflected i.e., if the electron is not deflected we cannot be sure that there is no magnetic field in that region.
Question 9
1 / -0

The distance between the supply wires of an electric-mains is $$12cm$$. These wires experience $$4mg$$ weight per unit length. Current flowing in both the wire will be if they carry current in same direction.

A
zero

B
$$4.85A$$

C
$$4.85A$$

D
$$4.85\times {10}^{-4}A$$

Solution
Question 10
1 / -0

A long, vertical, metallic wire carries downward electric current.
What would be the direction of the field if the current consisted of positive charges moving downward instead of electrons moving upward?

A
north

B
south

C
east

D
west

E
up

Solution

The direction of the magnetic field at a given point is determined by the direction of the conventional current that creates it.

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Moving Charges and Magnetism Test - 70

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Moving Charges and Magnetism Test - 70

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Question 1

Directly proportional to $$Q$$

Inversely proportional to $$Q$$

Inversely proportional to $$A$$

Directly proportional to $$A$$

Solution

Question 2

Lenz

Ampere

Ohm

Maxwell

Solution

Question 3

$$He^+$$ ions will be deflected more than those of $$O^{2+}$$

$$He^+$$ ions will be deflected less than those of $$O^{2+}$$

All the ions will be deflected equally

No ions will be deflected

Solution

Question 4

Ellipse

Circle

Parabola

None of these

Solution

Question 5

Attract each other

repel each other

No relation

Neither attract nor repel

Solution

Question 6

$$10^{-3}\ N$$

$$2.5 \times \ 10^{-3}\ N$$

Zero

$$1.5 \times 10^{-3}\ N$$

Solution

Question 7

Both will follow a circular path with same radius

Both will follow a helical path

Both will follow a parabolic path

All the statements ate false

Solution

Question 8

If both assertion and reason are true and the reason is the correct explanation of the assertion.

If both assertion and reason are true but reason is not the correct explanation of the assertion.

If assertion is true but reason is false.

If the assertion and reason both are false.

Iassertion is false but reason is true.

Solution

Question 9

zero

$$4.85A$$

$$4.85A$$

$$4.85\times {10}^{-4}A$$

Solution

Question 10

north

south

east

west

up

Solution

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