The Force F Experienced By A Particle Of Charge Q Moving With Velocity V In A Magnetic Field B Is Given By F.docx

17 - 02-2019

PHYSICS TEST – 12TH CLASS MAGNETIC EFFECTS OF CURRENT

TIME – 2HR

MARKS -42

⃗⃗ is given by 𝐹⃗ = 𝑞(𝑣⃗ × 1. The force 𝐹⃗ experienced by a particle of charge q moving with velocity 𝑣⃗ in a magnetic field 𝐵 ⃗⃗⃗). Which pair of vectors is always at right angles to each other? 𝑩 1 2. How can a moving coil galvanometer be converted into a voltmeter? 1 3. If the ratio of horizontal to vertical component of earth’s magnetic field is 1/√3 at a place, find the angle of dip. 2 4. Write SI unit of 2 a. Magnetic pole strength b. Magnetic dipole moment of a bar magnet. 5. Give two points to compare the magnetic properties of steel and soft iron. 2 6. An electron, after being accelerated through a potential difference of 100V, enters a uniform magnetic field of 0.004 T perpendicular to the direction of motion. Calculate the radius of the path described by electron (𝑒 = 1.6 × 10−19 𝐶 𝑎𝑛𝑑 𝑚 = 9.1 × 10−31 𝑘𝑔). 2 8 −3 7. An electron moving with a speed of 10 m/s enters a magnetic field of 5 × 10 𝑇 in a direction perpendicular to the field. Calculate 2 a. Radius of path b. Frequency of revolution of electron. 8. A beam of alpha particles and of the proton of the same velocity V, enter a uniform magnetic field at right angles to the field lines. The particles describe circular paths. What is the ratio of radii of these two circles? 2 9. Distinguish between diamagnetic and ferromagnetic materials in respect of 3 a. Intensity of magnetisation b. Behaviour of non – uniform magnetic field and c. Susceptibility 10. A rectangular loop of wire of size 4cm × 10cm carries a steady current of 2A. A straight long wire carrying 5A current is kept near the loop as shown. If the loop and the wire are coplaner, find 3 a. The torque acting on the loop b. The magnitude and direction of the force on the loop due to current carrying wire.

11. Explain with the help of a labelled diagram, the underlying principle, construction and working of a cyclotron. Discuss limitations of a cyclotron. 5 12. a. Using Bio – Savart law, derive an expression for the magnetic field due to a current carrying loop at a point along the axis of the loop. 3 b. A long straight conductor carries a steady current ‘𝐼’. The current is distributed uniformly across its cross – section of radius ‘a’. Plot a graph showing the variation of magnetic field ‘B’ produced by the conductor with the distance ‘r’ from the axis of the conductor in the region i. rb ROYAL INSTITUTE (COMMERCE AND SCIENCE) PUNJABI COLONY NARELA 981138987, 9213491945

13. a. describe an expression for the magnetic field at a point on the axis of a current carrying circular loop. 3 b. Two coaxial circular loops 𝐿1 𝑎𝑛𝑑 𝐿2 of radii 3 and 4 cm are placed as shown. What should be the magnitude and direction of the current in the loop 𝐿2 , so that the net magnetic field at the point O be zero?

14. a. with the help of a diagram, explain the principle and working of moving coil galvanometer. 5 b. What is the importance of a radial magnetic field and how is it produced? c. Why is it that while using a moving coil galvanometer as a voltmeter, a high resistance in series is required, whereas in an ammeter a shunt is used? 15. A bar magnet of magnetic moment 1.5 𝐽𝑇 −1lies aligned with the direction of a uniform magnetic field of 0.22 T. 3 a. What is the amount of work required by an external torque to turn the magnet so as to align its magnetic moment. i. Normal to the field direction, and ii. Opposite to the field direction? b. What is the torque on the magnet in case (i) and (ii). 16. A magnetic dipole is under the influence of two magnetic fields. The angle between the field direction is 60 ͦ and one of the field has a magnitude of 1.2 × 10−2 𝑇. If the dipole comes to stable equilibrium at an angle of 15 ͦ with this field, what is the magnitude of other field? 3

ROYAL INSTITUTE (COMMERCE AND SCIENCE) PUNJABI COLONY NARELA 981138987, 9213491945