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 -

1. depends on v and not on R

2. depends on R and not on v

3. is independent of both v and R

4. depends on both v and R

Subtopic:  Lorentz Force |
 82%
From NCERT
NEET - 2009
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The magnetic force acting on a charged particle of charge -2μC in a magnetic field of 2T acting in y-direction, when the particle velocity is 2i^+3j^×106 ms-1 is.

1. 8 N in -z-direction

2. 4 N in z-direction

3. 8 N in y-direction

4. 4 N in y-direction

Subtopic:  Lorentz Force |
 69%
From NCERT
NEET - 2009
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A galvanometer having a coil resistance of 60Ω 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 

(a) putting in series resistance of 240Ω

(b) putting in parallel resistance of 240Ω

(c) putting in series resistance of 15Ω

(d) putting in parallel resistance of 15Ω

Subtopic:  Conversion to Ammeter & Voltmeter |
 76%
From NCERT
NEET - 2009
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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 F1, F2 and F3 respectively and are in the plane of the paper and along with the directions shown the force on the segment QP is 

(a)F3+F1-F2

(b)F3-F12+F22

(c)F3-F12-F22

(d)F3-F1+F2

Subtopic:  Current Carrying Loop: Force & Torque |
 78%
From NCERT
NEET - 2008
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A particle mass m, charge Q, and kinetic energy T enter a transverse uniform magnetic field of induction B. After 3sec the kinetic energy of the particle will be : 

1. 3T

2. 2T

3. T

4. 4T

Subtopic:  Lorentz Force |
 86%
From NCERT
NEET - 2008
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A galvanometer of resistance 50Ω 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 

(a) 5050Ω

(b) 5550 Ω

(c) 6050 Ω

(d) 4450Ω

Subtopic:  Conversion to Ammeter & Voltmeter |
 62%
From NCERT
NEET - 2008
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 A narrow electron beam passes undeviated through an electric field E = 3×104 volt/m and an overlapping magnetic field B=2×10-3 Weber/m2. If electric field and magnetic field are mutually perpendicular. The speed of the electrons is 
1. \(60\) m/s                       
2. 10.3×107 m/s
3. 1.5×107 m/s             
4. 0.67×10-7 m/s

Subtopic:  Lorentz Force |
 89%
From NCERT
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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

1. 20 ms-1                  2. 40 ms-1 
3. 8 ms-1                    4. 5.5 ms-1

Subtopic:  Lorentz Force |
 92%
From NCERT
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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

(1)107 m/s                    

(2) 104 m/s

(3) 105 m/s                   

(4) 102 m/s 

Subtopic:  Lorentz Force |
 73%
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Order of q/m ratio of proton, α-particle and electron is

(a) e>p>α               (b) p>α>e

(c) e>α>p               (d) None of these

Subtopic:  Lorentz Force |
 73%
From NCERT
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