Moving Charges and Magnetism Test

Result

Moving Charges and Magnetism Test - 77

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Question 1
1 / -0

The magnetic force acting on a charged particle of charge -2 $$\mu C$$ in a magnetic field of 2T acting in y-direction. when the particle velocity is
$$\left( {2\widehat i + 3\widehat j} \right) \times 10^6 ms^{ - 1} $$

A
4 N in z direction

B
8 N in -z direction

C
8 N is y direction

D
8 N is z direction

Solution
Question 2
1 / -0

Two paths (path 1 and 2) followed by charge particles in magnetic field is shown in the figure. All the charge particles enters the magnetic field at A with equal kinetic energy. Choose the incorrect statement

A
If 1 is $$\alpha$$-particle then 2 may be deutron

B
If 1 is proton then 2 may be deutron

C
If 1 is $$\alpha$$-particle then 2 must be proton

D
If 1 is deutron then 2 may be proton

Solution

Since $$\alpha$$ particles $$(He^{2+})$$possesses greater charge than den-tron $$D^{1+}$$ it will be deflected more in a magnetic field since $$=Bqv$$ where greater charge implies greater force experienced.
Question 3
1 / -0

A long parallel straight conductors carry $$i_{1}$$ and $$i_{2}(i_{1} > i_{2})$$. When the currents are in same direction, the magnetic field at a point midway between the wires is $$20 \mu T$$. If the direction of $$i_{2}$$ is reversed, the field becomes $$50 \mu T.$$ The ratio of the current $$i_{1}/ i_{2}$$ is:

A
$$\dfrac{5}{2}$$

B
$$\dfrac{7}{3}$$

C
$$\dfrac{4}{3}$$

D
$$\dfrac{5}{3}$$

Solution
Question 4
1 / -0

The coil of a dynamo is rotating in a magnetic field. The developed induced emf changes and the number of magnetic lines of force also changes. Which of the following conditions is correct?

A
Lines of force minimum but induced emf is zero

B
Lines of force maximum but induced emf is zero

C
Lines of force maximum but induced emf is not zero

D
Lines of force maximum but induced emf is also maximum

Solution
Question 5
1 / -0

A particle is moving in a region having a uniform magnetic field and a parallel, uniform electric field. At some instant, the velocity of the particle is perpendicular to the field direction. The path of the particle will be

A
a straight line

B
a circle

C
a helix with uniform pitch

D
a helix with nonuniform pitch

Solution

Refer image 1.
The direction of the forces are
$$\rightarrow$$ upward-electric force
$$\rightarrow$$ right hand thumb rule- right hand side- magnetic force
Refer imag 2.
$$\bar{F}=m\bar{a}$$
So, the particle moves in a circular path of radius $$\boxed{r=\dfrac{mv}{qB}}$$
Refer image 3.
resultant would be a helical path with non-uniformed pitch
$$\downarrow$$
since velocity is non-uniform.
Question 6
1 / -0

A long straight wire carrying a current of 1.0 A is placed horizontally in a uniform magnetic field $$B = 1.0 \times 10 ^{-5} T$$ pointing vertically upwards (figure). The magnitude of the resultant magnetic field at the points P and Q, both situated at a distance of $$2.0 cm$$ from the wire in the same horizontal plane are respectively.

A
zero, $$20 \mu T$$

B
$$20 \mu T$$, zero

C
zero, zero

D
$$20 \mu T, 20 \mu T$$

Solution
Question 7
1 / -0

A beam of electrons moving along +y direction enters in a region of uniform electric and magnetic fields. If the beam goes undeflected through this region then field (B) and (E) are directed respectively:

A
-y axis and -z axis

B
+z axis and +xaxis

C
+ x axis and -x axis

D
- x axis and -y axis

Solution
Question 8
1 / -0

Two semi infinite wires AO and OC coinciding at O carry equal current I as shown in figure. Angle AOC is $$\alpha$$. The magnitude of magnetic field at a point P on the bisector of these two wires at a distance r from point O is

A
$$\frac{\mu_0 I}{2\pi r} cot \Bigg\lgroup \frac{\alpha}{2} \Bigg\rgroup$$

B
$$\frac{\mu_0 I}{4\pi r} cot \Bigg\lgroup \frac{\alpha}{2} \Bigg\rgroup$$

C
$$\frac{\mu_0 I}{2\pi r} \Bigg\lgroup cosec \Bigg\lgroup \frac{\alpha}{2} \Bigg\rgroup + cot \Bigg\lgroup \frac{\alpha}{2} \Bigg\rgroup \Bigg\rgroup$$

D
$$\frac{\mu_0 I}{4\pi r} sin \Bigg\lgroup \frac{\alpha}{2} \Bigg\rgroup$$

Solution
Question 9
1 / -0

Two particle of charges +Q and -Q are projected from the same point with a velocity v in a region of uniform magnetic field B such that the velocity vector makes $$\theta$$ with the magnetic field. Their masses are M and 2M respectively. Then, they will meet again for the first time at a point whose distance from the point of projection is

A
$$\dfrac{2\pi Mv \cos \theta}{QB}$$

B
$$\dfrac{8\pi Mv \cos \theta}{QB}$$

C
$$\dfrac{\pi Mv \cos \theta}{QB}$$

D
$$\dfrac{4 \pi Mv \cos \theta}{QB}$$

Solution
Question 10
1 / -0

Two particles of charges +Q and -Q are projected from the same point with a velocity v in a region of uniform magnetic field B such that the velocity vector makes an angle $$\theta $$ with the magnetic field.Their masses are M and 2M, respectively.Then,they will meet again for the first time at a point whose distance from the point of projection is

A
$$\dfrac { 2\pi Mvcos\theta }{ QB } $$

B
$$\dfrac { 8\pi Mvcos\theta }{ QB } $$

C
$$\dfrac { \pi Mvcos\theta }{ QB } $$

D
$$\dfrac { 4\pi Mvcos\theta }{ QB } $$

Solution