CBSE Class 12 Physics Moving Charges and Magnetism Worksheet Set A

CBSE Class 12 Physics Moving Charges and Magnetism Worksheet Set A

Question. A square loop, carrying a steady current I, is placed in a horizontal plane near a long straight conductor carrying a steady current I₁ at a distance d from the conductor as shown in figure. The loop will experience
(a) a net repulsive force away from the conductor
(b) a net torque acting upward perpendicular to the horizontal plane
(c) a net torque acting downward normal to the horizontal plane
(d) a net attractive force towards the conductor

Answer: D

Question. A current carrying conductor placed in a magnetic field experiences maximum force when angle between current and magnetic field is
(a) 3 π/4
(b) π/2
(c) π/4
(d) zero

Answer: B

Question. The field B at the centre of a circular coil of radius r is p times that due to a long straight wire at a distance r from it, for equal currents. Fig. shows three cases: in all cases the circular part has radius r and straight ones are infinitely long. For same current the field B at the centre P in cases 1, 2, 3 has the ratio
(a) (-π/2) : π/2 : (3π/4 - 1/2)
(b) (-π/2+1) : (π/2+1) : (3π/4 + 1/2)
(c) -π/2 : π/2 : 3π/4
(d) (-π/2 - 1) : (π/4 + 1/4) : (3π/4 + 1/2)

Answer: A

Question. A circular loop of area 0.02 m² carrying a current of 10A, is held with its plane perpendicular to a magnetic field induction 0.2 T. The torque acting on the loop is
(a) 0.01 Nm
(b) 0.001 Nm
(c) zero
(d) 0.8 Nm

Answer: C

Question. 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 : 

Answer: A

Question. An arrangement of three parallel straight wires placed perpendicular to plane of paper carrying same current 'I along the same direction is shown in fig. Magnitude of force per unit length on the middle wire 'B' is given by (19 ex 3)
(a) 2μ₀i²/πd
(b) √2μ₀i²/πd
(c) μ₀i²/√2πd
(d) μ₀i²/2πd

Answer: C

Question. In a cyclotron, a charged particle
(a) undergoes acceleration all the time
(b) speeds up between the dees because of the magnetic field
(c) speeds up in a dees
(d) slows down within a dee and speeds up between dees

Answer: A

Question. A uniform magnetic field acts at right angles to the direction of motion of electron. As a result, the electron moves in a circular path of radius 2cm. If the speed of electron is doubled, then the radius of the circular path will be
(a) 2.0 cm
(b) 0.5 cm
(c) 4.0 cm
(d) 1.0 cm

Answer: C

Question. A current loop consists of two identical semicircular parts each of radius R, one lying in the x-y plane and the other in 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
(a) μ₀i/√2R
(b) μ₀i/2√2R
(c) μ₀i/2R
(d) μ₀i/4R

Answer: B

Question. In cyclotron the gyro radius is
(a) proportional to momentum
(b) proportional to energy
(c) inversely proportional to momentum
(d) inversely proportional to energy

Answer: A

Question. A wire ABCDEF is bent in the form as shown in figure. The wire carries a current I and is placed in a uniform magnetic field of induction B parallel to positive Y-axis. If each side is of length L, the force experienced by the wire will be
(a) IBL along the positive Z-direction
(b) IBL along the negative Z-direction
(c) 2IBL along the positive Z-direction
(d) 2IBL along the negative Z-direction

Answer: A

Question. Three wires are situated at the same distance. A current of 1A, 2A, 3A flows through these wires in the same direction.
What is ratio of F₁/F₂ , where F₁ is force on 1 and F₂ on 2?
(a) 7/8
(b) 1
(c) 9/8
(d) None of these

Answer: A

Question. Two equal electric currents are flowing perpendicular to each other as shown in figure. AB and CD are perpendicular to each other and symmetrically placed with respect to the currents. Where do we expect the resultant magnetic field to be zero?
(a) on AB
(b) on CD
(c) on both AB & CD
(d) on both OD & BO

Answer: A

Question. A conducting circular loop of radius r carries a constant current i. It is placed in a uniform magnetic field B such that B is perpendicular to the plane of the loop. The magnetic force acting on the loop is :
(a) ir B
(b) 2πriB
(c) zero
(d) πriB

Answer: C

Question. A coil carrying electric current is placed in uniform magnetic field, then
(a) torque is formed
(b) e.m.f is induced
(c) both (a) and (b) are correct
(d) none of the above

Answer: A

Question. A charge moving with velocity v in X-direction is subjected to a field of magnetic induction in negative X-direction. As a result, the charge will
(a) remain unaffected
(b) start moving in a circular path Y–Z plane
(c) retard along X-axis
(d) move along a helical path around X-axis

Answer: A

Question. A very long straight wire carries a current I. At the instantwhen a charge + Q at point P has velocity V̅ , as shown, the force on the charge is 

(a) along oy
(b) opposite to oy
(c) along ox
(d) opposite to ox

Answer: A

Question. A straight wire of length 0.5 metre and carrying a current of 1.2 ampere is placed in uniform magnetic field of induction 2 tesla. The magnetic field is perpendicular to the length of the wire. The force on the wire is
(a) 2.4 N
(b) 1.2 N
(c) 3.0 N
(d) 2.0 N

Answer: B

Question. 1 Wbm^–2 is equal to
(a) 10⁴ G
(b) 10² G
(c) 10^–2 G
(d) 10^–4 G

Answer: A

Question. A moving coil galvanometer has a resistance of 900 Ω. In order to send only 10% of the main current through this galvanometer, the resistance of the required shunt is
(a) 0.9 Ω
(b) 100 Ω
(c) 405 Ω
(d) 90 Ω

Answer: B

Question. An electron is projected with uniform velocity along the axis of a current carrying long solenoid. Which of the following is true?
(a) The electron will be accelerated along the axis
(b) The electron path will be circular about the axis
(c) The electron will experience a force at 45° to the axis and hence execute a helical path
(d) The electron will continue to move with uniform velocity along the axis of the solenoid

Answer: D

Question. An electron moves in a circular orbit with a uniform speed v. It produces a magnetic field B at the centre of the circle. The radius of the circle is proportional to
(a) √B/v
(b) B/v
(c) √v/B
(d) v/B

Answer: D

Question. 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 2 I, respectively. The resultant magnetic field induction at the centre will be 
(a) √5μ₀I/2R
(b) 3μ₀I/2R
(c) μ₀I/2R
(d) μ₀I/R

Answer: A

Question. A proton and an alpha particle both enter a region of uniform magnetic field B, moving at right angles to 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: 
(a) 0.5 MeV
(b) 1.5 MeV
(c) 1 MeV
(d) 4 MeV

Answer: C
 

              Very Short Answer

Q1)       What is mass spectrometer?

Q2)       Who concluded that moving charges or currents produced a magnetic field in the surrounding space?

Q3)       Define radius of helix?

Q4)       What is gauss?

Q5)       Who realised that light were electromagnetic waves?

              Short Answer

Q6)       What is permittivity and permeability in magnetism?

Q7)       How magnetic force is different form electric force?

Q8)       What is the source of the magnetic forces?

Q9)       What do you mean by the term motion in a magnetic field?

Q10)     What do you mean by the term helical motion of charged particles and aurora borealis?

              Long Answer

Q11)     State the difference between magnetic field and electric field?

Q12)     Write short note on cyclotron?

Q13)     Explain Lorentz force and how it interacts with the magnetic field?

Q14)     State the difference between magnetism and electricity?

Q15)     What are the similarities and difference between Biot-Savart law and coulomb’s law?