When a charged particle moving with velocity v → is subjected to a magnetic field of induction B → , the force on it is non-zero. This implies that:

angle between v → and B → have any value other than zero and 180 o .

angle between v → and B → is necessarily 90 o .

angle v → and B → between can have any value other than 90 o .

angle between v → and B → is either zero or 180 o .

Physics - Moving Charges Magnetism - Quiz-7

Order of q/m ratio of proton, $α$ -particle and electron is
(a) $e > p > α$ (b) $p > α > e$

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1
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2
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3
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4

A straight conductor carrying current I splits into two parts as shown in the figure. The radius of the circular loop is R. The total magnetic field at the centre P of the loop is,

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zero
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$\frac{3 μ_{0} i}{32 R}, i n w a r d$
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$\frac{3 μ_{0} i}{32 R}, o u t w a r d$
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$\frac{μ_{0} i}{2 R}, i n w a r d$

$O^{+ +}, C^{+}, {He}^{+ +}$ and $H^{+}$ ions are projected on the photographic plate with the same velocity in a mass spectrograph. Which one will strike the farthest?

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$O^{+ +}$
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$C^{+}$
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${He}^{+ +}$
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$H_{2}^{+}$

A 250 turn rectangular coil of length 2.1 cm and width 1.25 cm carries a current of 85 $μA$ and subjected to the magnetic field of strength 0.85 T. Work done for rotating the coil by 180° against the torque is:

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$4.55 μ J$
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$2.3 μ J$
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$1.15 μ J$
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$9.8 μ J$

A metallic rod of mass per unit length 0.5 kg m^-1 is lying horizontally on a smooth inclined plane which makes an angle of 30° with the horizontal. The rod is not allowed to slide down by flowing a current through it when a magnetic field of induction 0.25 T is acting on it in the vertical direction. The current flowing in the rod to keep it stationery is:

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7.14 A
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5.98 A
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14.76 A
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11.32 A

The current sensitivity of a moving coil galvanometer is 5 div/mA and its voltage sensitivity (angular deflection per unit voltage applied) is 20 div/V. The resistance of the galvanometer is:

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40 $Ω$
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25 $Ω$
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250 $Ω$
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500 $Ω$

A square loop ABCD carrying a current i is placed near and coplanar with a long straight conductor XY carrying a current I, the net force on the loop will be:

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$\frac{μ_{o} Ii}{2 π}$
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$\frac{2 μ_{o} IiL}{3 π}$
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$\frac{μ_{o} IiL}{2 π}$
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$\frac{2 μ_{o} Ii}{3 π}$

A rectangular coil of length 0.12 m and width 0.1 m having 50 turns of wire is suspended vertically in a uniform magnetic field of strength 0.2 Wb/m². The coil carries a current of 2 A. If the plane of the coil is inclined at an angle of 30^o with the direction of the field, the torque required to keep the coil in stable equilibrium will be:

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0.15 Nm
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0.20 Nm
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0.24 Nm
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0.12 Nm

A wire carrying current I 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. The magnetic field at point O is:

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$B = \frac{μ_{o} i}{4 πR} (π \hat{i} + 2 \hat{k})$
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$B = - \frac{μ_{o} i}{4 πR} (π \hat{i} - 2 \hat{k})$
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$B = - \frac{μ_{o} i}{4 πR} (π \hat{i} + 2 \hat{k})$
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$B = \frac{μ_{o} i}{4 πR} (π \hat{i} - 2 \hat{k})$

An electron moving in a circular orbit of radius r makes n rotations per second. The magnetic field produced at the centre has a magnitude:

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μ₀ne/2πr
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zero
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_n²e/r
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μ₀ne/2r

The resistance of an ammeter is 13 Ω and its scale is graduated for a current up to 100 A. After an additional shunt has been connected to this ammeter, it becomes possible to measure currents up to 750 A by this ammeter. The value of shunt resistance is:

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20 $Ω$
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2 $Ω$
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0.2 $Ω$
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2 k $Ω$

A charged particle (charge q) is moving in a circle of radius R with uniform speed v. The associated magnetic moment μ is given by:

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$\frac{qvR}{2}$
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${qvR}^{2}$
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$\frac{{qvR}^{2}}{2}$
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$qvR$

In a mass spectrometer used for measuring the masses of ions, the ions are initially accelerated by an electric potential V and then made to describe semi-circular paths of radius R using a magnetic field B. If V and B are kept constant, the ratio $\frac{Charge on the ion}{mass of the ion}$ , will be proportional to:

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$\frac{1}{R}$
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$\frac{1}{R^{2}}$
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$R^{2}$
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R

A beam of electrons passes un-deflected through mutually perpendicular electric and magnetic fields. If the electric field is switched off, and the same magnetic field is maintained, the electrons move:

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in an elliptical orbit.
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in a circular orbit.
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along a parabolic path.
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along a straight line.

When a charged particle moving with velocity $\vec{v}$ is subjected to a magnetic field of induction $\vec{B}$ , the force on it is non-zero. This implies that:

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angle between $\vec{v}$ and $\vec{B}$ is necessarily 90^o.
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angle $\vec{v}$ and $\vec{B}$ between can have any value other than 90^o.
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angle between $\vec{v}$ and $\vec{B}$ have any value other than zero and 180^o.
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angle between $\vec{v}$ and $\vec{B}$ is either zero or 180^o.

Two circular coils 1 and 2 are made from the same wire but the radius of the 1^st coil is twice that of the 2^nd coil. What is the ratio of the potential difference applied across them so that the magnetic field at their centres is the same?

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3
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4
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6
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2

A cylindrical conductor of radius R is carrying a constant current. The plot of the magnitude of the magnetic field B with the distance d from the centre of the conductor is correctly represented by the figure:

Ionized hydrogen atoms and $α$ -particles with the same momenta enter perpendicular to a constant magnetic field, B. The ratio of their radii $r_{H} : r_{α}$ of their paths will be:

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1 : 4
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2 : 1
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1 : 2
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4 : 1

Adjoining figure shows a rectangular loop of conductor carrying a current i. The length and breadth of the loop are respectively a and b. The magnetic field at the centre of loop is:-

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$\frac{μ_{0} i (a + b)}{2 π \sqrt{a^{2} + b^{2}}}$
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$\frac{μ_{0} i a b}{2 π \sqrt{a^{2} + b^{2}}}$
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$\frac{μ_{0} i (a + b)}{π \sqrt{a^{2} + b^{2}}}$
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$\frac{2 μ_{0} i \sqrt{a^{2} + b^{2}}}{π a b}$

A milliammeter of range 10 mA and resistance 9 $Ω$ is joined in a circuit as shown in Fig. 6.57. The meter gives full-scale deflection for current I when A and C are used as its terminals if current enter at A and leaves at C (B is left isolated). The value of I is :

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100 mA
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900 mA
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1 A
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1.1 A

A candidate connects a moving coil voltmeter V, a moving coil ammeter A, and a resistor R as shown in Fig. 6.58. If the voltmeter reads 20 V and the ammeter reads 4 A, R is

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equal to 5 $Ω$
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greater than 5 $Ω$
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less than 5 $Ω$
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greater or less than 5 $Ω$ depending upon its material.

A galvanometer has a resistance of 3663 $Ω$ . A shunt S is connected across it such that 1/34 of the total current passes through the galvanometer. The value of the shunt is :

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3663 $Ω$
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111 $Ω$
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107.7 $Ω$
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3555.3 $Ω$

Two toroids 1 and 2 have total no. of turns 200 and 100 respectively with average radii 40 cm and 20 cm respectively. If they carry the same current i, the ratio of the magnetic fields along the two loops is:

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1:1
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4:1
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2:1
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1:2

Three infinitely-long conductors carrying currents $I_{1}, I_{2} a n d I_{3}$ lie perpendicular to the plane of the paper as shown below.

If the value of integral $\oint \vec{B} . \vec{dl}$ for the loops $C_{1}, C_{2} and C_{3} are 2 μ_{0}, 4 μ_{0} and μ_{0}$ in the units of N/A, respectively, then

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$I_{1}$ = 3 A into the paper
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$l_{2}$ = 3 A out of the paper
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$I_{3}$ = 0
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$I_{3}$ = 1 A out of the paper

In the cosmic shower, an electron is falling towards the earth near the equator. In which direction will it be deflected?

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Eastward
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Westward
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Northward
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Southward

The endpoints of a current-carrying wire lie on the x-axis and y-axis as shown. The magnetic force on the wire is:

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Zero
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6 N
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8 N
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10 N

The given figure shows a semicircular loop of radius R carrying current I and is placed in a uniform magnetic field B. The force acting on the semicircular part of the loop is

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$B_{0} π l R$
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$2 πlRB$
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$l R B$
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$2 l R B$

A non-conducting rod AB of length L has a positive linear charge density $λ$ . This rod is rotated about its one end with an angular speed $ω$ as shown. The magnetic moment associated with this rod is-

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λ $\frac{L^{3} ω}{3}$
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λ $\frac{L^{3} ω}{6}$
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$\frac{π L^{3} ω}{12}$
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$\frac{π L^{3} ω}{24}$

A charge is moving in a circular path of radius 'r' with speed v in a transverse magnetic field B. Specific charge of the particle is

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$\frac{v}{B r}$
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$\frac{B}{v r}$
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Bvr
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$\frac{v r}{B}$

Voltage sensitivity of a moving coil galvanometer is $V_{s}$ and current sensitivity is $I_{s}$ . Resistance of galvanometer is 'G'. The relation between $V_{s} and I_{s}$ is :

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$V_{s} = \frac{l_{s}}{G}$
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$V_{s} = l_{s} . G$
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$\frac{G}{V_{s} I_{s}} = V_{s}$
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$\frac{G}{V_{s}} = I_{s}$

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Practice Physics Quiz Questions and Answers

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Practice Physics Quiz Questions and Answers

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