A particle having a mass of 10 - 2 kg carries a charge of 5 × 10 - 8 C . The particle is given an initial horizontal velocity of 10 5 ms - 1 in the presence of electric field E → and magnetic field B → . To keep the particle moving in a horizontal direction, it is necessary that (1) B → should be perpendicular to the direction of velocity and E → should be along the direction of velocity. (2) Both B → and E → should be along the direction of velocity. Which one of the following pairs of statements are possible?

(3) Both B → and E → are mutually perpendicular and perpendicular to the direction of velocity.

(4) B → should be along the direction of velocity and E → should be perpendicular to the direction of velocity.

Physics - Moving Charges Magnetism - Quiz-6

A long straight wire of radius 'a' carries a steady current I. The current is uniformly distributed over its cross-section. The ratio of the magnetic fields B and B' at radial distances a/2 and 2a respectively, from the axis of the wire, is:

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1/2
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1
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4
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1/4

A wire carrying current l has the shape as shown in the adjoining figure. Linear parts of the wire are very long and parallel to X-axis while the semicircular portion of radius R is lying in the Y-Z plane. Magnetic field at point O is :

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$B = \frac{μ_{0}}{4 π} \times \frac{i}{R} (π \hat{i} + 2 \hat{k})$
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$B = - \frac{μ_{0}}{4 π} \times \frac{i}{R} (π \hat{i} - 2 \hat{k})$
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$B = - \frac{μ_{0}}{4 π} \times \frac{i}{R} (π \hat{i} + 2 \hat{k})$
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$B = \frac{μ_{0}}{4 π} \times \frac{i}{R} (π \hat{i} - 2 \hat{k})$

An electron moving in a circular orbit of radius r makes n rotations per second. The magnetic field produced at the centre has magnitude:
$1 . \frac{μ_{0} n e}{2 π r} 2 . Z e r o 3 . \frac{n^{2} e}{r} 4 . \frac{μ_{0} n e}{2 r}$

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1
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2
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3
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4

A proton and an alpha particle both enter a region of uniform magnetic field B, moving at right angles to the field B. If the radius of circular orbits for both the particles is equal and the kinetic energy acquired by proton is 1 MeV, the energy acquired by the alpha particle will be

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4 MeV
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0.5 MeV
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1.5 MeV
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1 MeV

A circuit contains an ammeter, a battery of 30 V and a resistance 40.8Ω all connected in series. If the ammeter has a coil of resistance 480Ω and a shunt of 20Ω then reading in the ammeter will be :

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0.5A
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0.25A
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2A
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1A

Two identical long conducting wires AOB and COD are placed at right angle to each other, with one above other such that O is their common point for the two. The wires carry I₁and I₂ currents, respectively. Point P is lying at distance d from 0 along a direction perpendicular to the plane containing the wires. The magnetic field at the point P will be

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μ_o/2πd(I₁/I₂)
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μ_o/2πd (I₁+I₂)
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μ_o/2πd(I₁²-I₂²)
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μ_o/2πd(I₁²+I₂²)^1/2

A current loop in a magnetic field

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experiences a torque whether the field is uniform or non-uniform in all orientations
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can be in equilibrium in one orentations.
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can be equilibrium in two orientations, both the wquilibriu states are unstable
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can be in equilibrium in two orientations, one stable while the other is unstable

Two similar coils of radius R are lying concentrically with their planes at right angles to each other. The currents flowing in them are I and 2I, respectively. The resultant magnetic field induction at the centre will be

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$\frac{\sqrt{5} μ_{0} I}{2 R}$
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$\frac{3 μ_{0} I}{2 R}$
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$\frac{μ_{0} I}{2 R}$
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$\frac{μ_{0} I}{R}$

A millivoltmeter of 25 mV range is to be converted into an ammeter of 25 A range. The value (in ohm) of necessary shunt will be:

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0.001
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0.01
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1
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0.05

An alternating electric field of frequency v, is applied across the dees (radius=R) of a cyclotron that is being used to accelerate protons(mass=m).The operating magnetic field (B) used in the cyclotron and the kinetic energy (K) of the proton beam, produced by it, are given by

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B= $\frac{m v}{e} a n d K = 2 m π^{2} v^{2} R^{2}$
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B= $\frac{2 π m v}{e} a n d K = m^{2} {πvR}^{2}$
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B= $\frac{2 π m v}{e} a n d K = 2 m π^{2} v^{2} R^{2}$
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B= $\frac{m v}{e} a n d K = m^{2} {πvR}^{2}$

A proton carrying 1 MeV kinetic energy is moving in a circular path of radius R in a uniform magnetic field. What should be the energy of an $α$ -particle to describe a circle of the same radius in the same field?

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2 MeV
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1 MeV
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0.5 MeV
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4 MeV

A current-carrying closed loop in the form of a right-angle isosceles triangle ABC is placed in a uniform magnetic field acting along AB. If the magnetic force on the arm BC is F, the force on the arm AC is:

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$- F$
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$F$
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$\sqrt{2} F$
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$- \sqrt{2} F$

A galvanometer of resistance, G is shunted by a resistance S ohm. To keep the main current in the circuit unchanged, the resistance to be put in series with the galvanometer is

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$\frac{S^{2}}{(S + G)}$
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$\frac{S G}{(S + G)}$
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$\frac{G^{2}}{(S + G)}$
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$\frac{G}{(S + G)}$

A square loop, carrying a steady current I, is placed in a horizontal plane near a long straight conductor carrying a steady current $I_{1}$ at a distance d from the conductor as shown in figure. The loop will experience

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a net repulsive force away from the conductor
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a net torque acting upward perpendicular to the horizontal plane
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a net torque acting downward normal to the horizontal plane
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a net attractive force towards the conductor

Charge q is uniformly spread on a thin ring of radius R. The ring rotates about its axis with a uniform frequency f Hz. The magnitude of magnetic induction at the center of the ring is :

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$\frac{μ_{0} q f}{2 R}$
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$\frac{μ_{0} q}{2 f R}$
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$\frac{μ_{0} q}{2 π f R}$
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$\frac{μ_{0} q f}{2 πR}$

A beam of cathode rays is subjected to crossed Electric (E) and magnetic fields(B). The fields are adjusted such that the beam is not deflected. The specific charge of the cathode rays is given by:

(where V is the potential difference between cathode and anode)

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$\frac{B^{2}}{2 V E^{2}}$
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$\frac{2 V B^{2}}{E^{2}}$
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$\frac{2 V E^{2}}{B^{2}}$
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$\frac{E^{2}}{2 V B^{2}}$

A galvanometer has a coil of resistance $100 Ω$ and gives a full scale deflection for 30 mA current.If it is to work as a voltmeter of 30V range, the resistance required to be added will be

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900 $Ω$
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1800 $Ω$
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500 $Ω$
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1000 $Ω$

A square current carrying loop is suspended in a uniform magnetic field acting in the plane of the loop. If the force on one arm of the loop is $\vec{F}$ , the net force on the remaining three arms of the loop is

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3 $\vec{F}$
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$-$ $\vec{F}$
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$-$ 3 $\vec{F}$
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$\vec{F}$

A current loop consists of two identical semicircular parts each of radius R, one lying in the x-y plane, and the other in the x-z plane. If the current in the loop is i. The resultant magnetic field due to the two semicircular parts at their common centre is:

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$\frac{μ_{0} i}{2 \sqrt{2} R}$
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$\frac{μ_{0} i}{2 R}$
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$\frac{μ_{0} i}{4 R}$
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$\frac{μ_{0} i}{\sqrt{2} R}$

A closely wound solenoid of 2000 turns and area of cross-section $1.5 \times 10^{- 4} m^{2}$ carries a current of $2.0 A .$ It is suspended through its centre and perpendicular to its length, allowing it to turn in a horizontal plane in a uniform magnetic field $5 \times 10^{- 2} T$ making an angle of $30 °$ with the axis of the solenoid. The torque on the solenoid will be

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$3 \times 10^{- 3} N ‐ m$
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$1.5 \times 10^{- 3} N ‐ m$
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$1.5 \times 10^{- 2} N ‐ m$
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$3 \times 10^{- 2} N ‐ m$

A particle having a mass of $10^{- 2} kg$ carries a charge of $5 \times 10^{- 8} C .$ The particle is given an initial horizontal velocity of $10^{5} {ms}^{- 1}$ in the presence of electric field $\vec{E}$ and magnetic field $\vec{B}$ . To keep the particle moving in a horizontal direction, it is necessary that

(1) $\vec{B}$ should be perpendicular to the direction of velocity and $\vec{E}$ should be along the direction of velocity.

(2) Both $\vec{B}$ and $\vec{E}$ should be along the direction of velocity.

Which one of the following pairs of statements are possible?

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(1) and (3) 2. (3) and (4)
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3. (2) and (3) 4. (2) and (4)
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(3) Both $\vec{B}$ and $\vec{E}$ are mutually perpendicular and perpendicular to the direction of velocity.
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(4) $\vec{B}$ should be along the direction of velocity and $\vec{E}$ should be perpendicular to the direction of velocity.

Under the influence of a uniform magnetic field, a charged particle moves with constant speed v in a circle of radius R. The time period of rotation of the particle -

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depends on v and not on R
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depends on R and not on v
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is independent of both v and R
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depends on both v and R

The magnetic force acting on a charged particle of charge $- 2 μ C$ in a magnetic field of 2T acting in y-direction, when the particle velocity is $(2 \hat{i} + 3 \hat{j}) \times 10^{6} m s^{- 1}$ is.

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8 N in -z-direction
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4 N in z-direction
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8 N in y-direction
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8 N in z-direction

A galvanometer having a coil resistance of $60 Ω$ shows full scale deflection when a current of 1.0A passes through it. It can be converted into an ammeter to read currents upto 5.0A by

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() putting in series resistance of 240 $Ω$
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() putting in parallel resistance of 240 $Ω$
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() putting in series resistance of 15 $Ω$
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() putting in parallel resistance of 15 $Ω$

A closed-loop PQRS carrying a current is placed in a uniform magnetic field. If the magnetic forces on segments PS, SR and RO are $F_{1}, F_{2} a n d F_{3}$ respectively and are in the plane of the paper and along with the directions shown the force on the segment QP is

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() $F_{3} + F_{1} - F_{2}$
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() $\sqrt{{(F_{3} - F_{1})}^{2} + F_{2}^{2}}$
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() $\sqrt{{(F_{3} - F_{1})}^{2} - F_{2}^{2}}$
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() $F_{3} - F_{1} + F_{2}$

A particle mass m, charge Q, and kinetic energy T enter a transverse uniform magnetic field of induction $\vec{B}$ . After 3sec the kinetic energy of the particle will be :

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3T
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2T
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T
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4T

A galvanometer of resistance 50 $Ω$ is connected to a battery of 3 V along with a resistance of 2950 $Ω$ in series. A full-scale deflection of 30 divisions is obtained in the galvanometer. In order to reduce this deflection to 20 divisions, the resistance in series should be

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() 5050 $Ω$
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() 5550 $Ω$
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() 6050 $Ω$
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() 4450 $Ω$

A narrow electron beam passes undeviated through an electric field E = $3 \times 10^{4} volt / m$ and an overlapping magnetic field $B = 2 \times 10^{- 3} Weber / m^{2}$ . If electric field and magnetic field are mutually perpendicular. The speed of the electrons is

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60 m/s
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$10.3 \times 10^{7} m / s$
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$1.5 \times 10^{7} m / s$
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$0.67 \times 10^{- 7} m / s$

A beam of electrons is moving with constant velocity in a region having electric and magnetic fields of strength $20 {Vm}^{- 1}$ and 0.5 T at right angles to the direction of motion of the electrons. What is the velocity of the electrons

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20 ${ms}^{- 1}$
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40 ${ms}^{- 1}$
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8 ${ms}^{- 1}$
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5.5 ${ms}^{- 1}$

In Bainbridge mass spectrograph a potential difference of 1000 V is applied between two plates distant 1 cm apart and magnetic field in B = 1T. The velocity of undeflected positive ions in m/s from the velocity selector is

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$10^{7} m / s$
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$10^{4} m / s$
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$10^{5} m / s$
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$10^{2} m / s$

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Practice Physics Quiz Questions and Answers

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Practice Physics Quiz Questions and Answers

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