InterviewSolution
Saved Bookmarks
InterviewSolution
This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
A closely wound coil has a radius of 6.00 cm and carries a current of `2.50 A`. How many turns must it have if, at a point on the coil axis `6.00 cm` from the centre of the coil, the magnetic field is `6.39 xx 10^-4T` ? |
|
Answer» Correct Answer - [69] |
|
| 2. |
A small coil of radius 0.002 m is placed on the axis of a magnet of magnetic moment `10^(5)` `JT^(-1)` and length 0.1 m at a distance of 0.15 m from the centre of the magnet. The plane of the coil is perpendicular to the axis of the magnet. Find the force on the when a current of 2.0 A is passed through it. |
|
Answer» Correct Answer - `[43.96 xx 10^(-4)N]` |
|
| 3. |
A magnet is suspended at an angle `60^(0)` in an external magnetic field of `5xx10^(-4)T`. What is the work done by the magnetic field in bringing it in its direction? `["The magnetic moment"=20A-m^(2)]` |
|
Answer» Correct Answer - `[-5 xx 10^(-3)]` |
|
| 4. |
A magnet is suspended in the magnetic meridian with an untwisted wire. The upper end of wire is rotated through `180^(@)` to deflect the magnet by `30^(@)` from magnetic meridian. When this magnet is replaced by another magnet, the upper end of wire is rotated through `270^(@)` to deflect the magnet `30^(@)` from magnetic meridian. The ratio of magnetic moment of magnets is |
|
Answer» Correct Answer - `[M_(1) : M_(2) = 5:8]` |
|
| 5. |
A small magnet of magnetic moment `pixx10^(-3) Am^(2)` is placed on the Y-axis at a distance of 0.1 from the origin with its axis parallel to the X-axix. A coil have 169 turns and radius 0.05 m is placed on the X-axis at a distance of 0.12 m from the origin with the axis of the coil coinciding with the X-axis. Find the magnitude and direction of the current in the coil for a compass needle placed at the origin, to point in the north-south direction. |
|
Answer» Correct Answer - [`2.6 xx 10^(-10) A`, clockwise direction when viewed from O] |
|
| 6. |
A short magnet porduces a deflection of `30^(@)` when placed at certain distance in tanA position of magnetometer. If another short magnet of double the length and thrice the pole strength is placed at the same distance in tan B position of the magnetometer, the deflection produced will be- |
|
Answer» Correct Answer - `[60^(@)]` |
|
| 7. |
A wire carrying current `i` has the configuration as shown in figure. Two semi-infinite straight sections, both tangent to the same circle, are connected by a circular arc of central angle theta, along the circumference of the circle, with all sections lying in the same plane. What must be for `B` to be zero at the centre of the circle? |
|
Answer» Correct Answer - [2 rad] |
|
| 8. |
The force experienced by a pole of strength 100 Am at a distance of 0.2 m from a short magnet of length 5 cm and pole strength of 200 Am on its axial line will be |
|
Answer» Correct Answer - `[2.5 xx 10^(-2)N]` |
|
| 9. |
A magnet of length `0.1 m` and pole strength `10^(-4)` A.m. is kept in a magnetic field of `30 Wb//m^(2)` at an angle `30^(@)`. The couple acting on it is `…xx10^(-4)Nm`. |
|
Answer» Correct Answer - `[1.5 xx 10^(-4)"Nm"]` |
|
| 10. |
Find the magnetic induction vector at origin O due to the current carrying wire configuration as shown in figure-4.33. |
|
Answer» Correct Answer - `[(mu_(0)I)/(4 pi a)[hat(i) - (pi)/(2) hat(j) - 2 hat(k)]]` |
|
| 11. |
The strength of the magnetic field around a long straight current carrying conductor :A. Is same everywhere around the conductorB. Obeys inverse square lawC. Is directlyproportional to the square of the distance from the cnductorD. None of the above |
|
Answer» Correct Answer - D |
|
| 12. |
A wire of 60 cm length and mass 16 gm is suspended by a pair of flexible leads in a magnetic field of induction 0.40 T. What are the magnitude and direction of the current required to remove the tension in the supporting leads? |
|
Answer» Correct Answer - [0.41 A left to right] |
|
| 13. |
A straight segment `OC`(of length L meter) of a circuit carrying a current `I amp` is placed along the ` x- axis` ( fig.). Two infinetely long straight wires ` A and B` , each extending from ` z = -oo to +oo`, are fixed at ` y = -ameter and y = +a meter` respectively, as shown in the figure. If the wires ` A and B` each carry a current `I amp` into the plane of the paper, obtain the expression for the force acting on the segment ` OC`. What will be the force on `OC` if the current in the wire `B` is reversed? |
|
Answer» Correct Answer - `[(mu_(0)I^(2))/(2pi)ln((I^(2)+a^(2))/(a^(2))), 0]` |
|
| 14. |
A current `I = sqrt2` A flows in a circuit having the shape of isosceles trapezium. The ratio of the bases of the trapezium is 2. Find the magnetic induction B at symmetric point O in the plane of the trapezium. The length of the smaller base of the trapezium is `100 mm` and the distance `r=50mm`. |
|
Answer» Correct Answer - `[2xx 10^(-6)T]` |
|
| 15. |
Two long parallel wires carrying current ` 2.5 amperes` and `I ampere` in the same direction ( directed into the plane of the paper) are held at `P and Q` respectively such that they are perpendicular to the plane of paper. The points `P and Q` are located at a distance of ` 5 metres and 2 metres` respectively from a collinear point `R` ( see figure) (i) An electron moving with a velocity of ` 4xx10^(5) m//s ` along the positive ` x- direction ` experiences a force of magnitude `3.2xx10^(-20) N` at the point `R`. Find the value of `I`. (ii) Find all the positions at which a third long parallel wire carrying a current of magnitude `2.5 amperes` may be placed so that the magnetic induction at `R` is zero. |
|
Answer» Correct Answer - [4A] |
|
| 16. |
In a right handed coordinate system XY plane is horizontal and Z-axis is vertically npward. A uniform magnetic field exist in space in vertically npward direction with magnetic induction B. A particle with mass m and charge q is projected from the origin of the coordinate system at `t= 0` with a velocity vector given as `vec(v) = v_(1) hat(i) + v_(2) hat(k)` Find the velocity vector of the particle after time t. |
|
Answer» Correct Answer - `[(mv_(1))/(qB) sin ((qBt)/(m)), - (mv_(1))/(qB) (1 - cos ((qBt)/(m))), v_(2) t]` |
|
| 17. |
Each of the lettered points at the corners of the cube as shown in Fig. 1.60 represents a positive charge q moving with a velocity of magnitude v in the direction indicated. The region in the figure is in a uniform magnetic field `vec B`, parallel to the x-axis and directed toward right. Copy the figure, find the magnitude and direction of the force on each charge and show the force in your diagram. |
|
Answer» Correct Answer - [(a) `-qvB hat(k)` ; (b) `+qvB hat(j)` ; (c) Zero ; (d) `(-qvB)/(sqrt(2)) hat(j)` ; (e) `(-(qvB)/(sqrt(2)))(hat(j)+hat(k))`] |
|
| 18. |
The distance between the two plates of a cathode-ray oscilloscope is 1 cm and the potential difference between them is 1200 V. If an electron of energy 2000 eV enters at right angles to the field, what will be its deflection if the plate be 1.5 cm long. |
|
Answer» Correct Answer - [0.34 cm] |
|
| 19. |
Figure shows a wire AB of mass m placed on a rough inclined plane of inclination `alpha` and static friction coefficient `mu`. The wire carries a current I. Find the minimum magnitude of magnetic induction required to slide the wire up the inclined plane if direction of magnetic induction is normal to plane as shown in figure. |
|
Answer» Correct Answer - `[(mg (sin alpha + mu cos alpha))/(n)]` |
|
| 20. |
A `15000 V` electron is describing a circle in a uniform field of magnetic indnction 250G acting at right angle to it. Calculate tbe radius oftbe circle. |
|
Answer» Correct Answer - [1.66 cm] |
|
| 21. |
A wire shaped to a regular hexagon of side `2 cm` carries a current of `2A`. Find the magnetic field at the cetre of the hexagon. |
|
Answer» Correct Answer - `[1.38 xx 10^(-4) T]` |
|
| 22. |
A Rowland ring of mean radius 15 cm has 4500 turns of wire wound on a ferromagnetic core of relative permeability 800. Find the magnitnde of the magnetic field in the core for a magnetising current of 1.2 A. |
|
Answer» Correct Answer - [5.76 T] |
|
| 23. |
An `alpha-`particle is accelerated by a potential difference of `10^4 V.` Find the change in its direction of motion, if it enters normally in a region of thickness 0.1 m having transverse magnetic induction of 0.1 tesla. (Given: mass of `alpha-`particle `6.4xx10^(-27)`kg). |
|
Answer» Correct Answer - `[theta = 30^(@)]` |
|
| 24. |
A proton of charge `e` and mass `m` enters a uniform magnetic field `B = Bi` with an initial velocity `v=v_xhati+v_yhatj`. Find an expression in unit vector notation for its velocity at time `t`. |
|
Answer» Correct Answer - `[vec(v)=v_(x)hat(i)+v_(y)cos omega hat(j)-v_(y)sin omega t hat(k), Here omega=(Be)/(m)]` |
|
| 25. |
A beam of electrons enters a uniform magnetic field of `0*3T` with a velocity of `4xx10^5ms^-1` at an angle of `60^@` to the field. Find the radius of the helical path taken by the beam. Also find the pitch of the helix (distance travelled by a proton parallel to the magnetic field during one period of rotation). Mass of proton is `1*67xx10^(-27)kg`. |
|
Answer» Correct Answer - [12 mm, 43.7 mm] |
|
| 26. |
An electron moving with a velocity `10^(8) m//s` enters a magnetic field at an angle of `20^(@)` to the direction of the field. Calculate (a) The value of magnetic induction so that the helical path radius will be 2m. (b) The time required to execute one revolution of the helical path. (c) The pitch o fhelical path followed by the electron. |
|
Answer» Correct Answer - [(a) `9.6 xx 10^(-5) T`; (b) `3.69 xx 10^(-7)s`; (c) 34.68m] |
|
| 27. |
A beam of charged particle, having kinetic energy `10^3 eV`, contains masses `8xx10^(-27) kg and 1.6xx10^(-26) kg` emerge from the end of an accelerator tube. There is a plate at distance `10^2 m` from the end of the tube and placed perpendicular to the beam. Calculate the magnitude of the smallest magnetic field which can prevent the beam from striking the plate. |
|
Answer» Correct Answer - `[sqrt(2)T]` |
|
| 28. |
Consider the current carrying loop shown in figure formed of radial lines and segments of circles whose centres are at point `P`. Find the magnitude and direction of B at point P. |
|
Answer» Correct Answer - [`(mu_(0)i)/(12)((1)/(a)-(1)/(b))` out of the page] |
|
| 29. |
A galvanometer coil `5 cm xx 2 cm` with 200 turns is suspended vertically in a field of `5 xx 10^-2 T`. The suspension fibre needs a torque of `0.125 x10^-7 N -m` to twist it through one radian. Calculate the strength of the current required to be maintained in the coil if we require a deflection of `6^@`. |
|
Answer» Correct Answer - `[1.3 xx 10^(-7)A]` |
|
| 30. |
A coil al a moving Coil galvanometer twists through `90^@` when a current of one microampere is passed through it. If the area of the coil is `10^-4 m^2` and it has `100` turns, calculate the magnetic field of the magnet of the galvanometer. Given, `k = 10^-8N -m /degree.` |
|
Answer» Correct Answer - [90T] |
|
| 31. |
A 2 keV positron is projected into uniform field of induction B of `0.10 T` with its velocity vector making an angle of `89^(@)` with B. Convince your-self that the path will be a helix, its axis being the direction ofB. Find the period, the pitch `p`, and the radiusr of the helix, see figure-4.250. |
|
Answer» Correct Answer - [(1) `3.6 xx 10^(-10)s`, (2), `0.17 xx 10^(-3) m`, (3) `1.5 xx 10^(-3)` m] |
|
| 32. |
Figure given in the question is a cross-sectional view of a coaxial cable. The centre conductor is surrounded by a rubber layer, which is surrounded by an outer conductor, which is surrounded by another rubber layer. The current in the inner conductor is `1.0 A` out of the page, and the current in the outer conductor is 3.0A into the page. Determine the magnitude and direction of the magnetic field at points a and b. |
|
Answer» Correct Answer - [`200 mu T` toward the top of the page, `133 mu T` toward the bottom of the page] |
|
| 33. |
A thin, `50.0 cm` long metal bar with mass `750 g` rests on, but is not attached to, two metal supports in a `0.450 T` magnetic field as shown in figure. A battery and a resistance `R = 25.0Omega` in series are connected to the supports. (a) What is the largest voltage the battery can have without breaking the circuit at the supper(b) The battery voltage has this maximum value calculated. Decreasing the resistance to `2.0 Omega` the initial acceleration of the bar. |
|
Answer» Correct Answer - [(a) 817.5 V (b) `112.8 m//s^(2)`] |
|
| 34. |
A long cylinder of uniform cross section and radius R is carrying a current i along its length and current density is uniform cross section and radius r in the cylinder parallel to its length. The axis of the cylinderical cavity is separated by a distance d from the axis of the cylinder. Find the magnetic field at the axis of cylinder. |
|
Answer» Correct Answer - `[(mu_(0)I r^(2))/(2 pi d (R^(2) - r^(2)))]` |
|
| 35. |
A particle of mass m and charge + q is projected from origin with velocity `vec(V)=V_(0)hati` in a magnetic field `vec(B)=-(B_(0)x)hatk.` Here `V_(0)` and `B_(0)` are positive constants of proper dimensions. Find the radius of curvature of the path of the particle when it reaches maximum positive x co-ordinate. |
|
Answer» Correct Answer - [`sqrt((2mv_(0))/(B_(0)q))`] |
|
| 36. |
A thin conducting strip of width his tightly wound in the shape of a very long cylindrical coil with cross-sectional radius R to make a single layer straight solenoid as shown in figure-4.81. A direct current `I` flows through the strip. Find the magnetic induction inside and outside the solenoid as a function of the distance r from its axis. |
|
Answer» Correct Answer - `[(mu_(0)I)/(h) sqrt(1 - ((h)/(2pi T))^(2)), (mu_(0)I)/(2pi r)]` |
|
| 37. |
A coil in the shape of an equilateral triangle of side 0.02 m is suspended from a vertex such that it is hanging in a vertical plane between the pole pieces of a permanent magnet producing a horizontal magnetic field of `5 xx 10^(-2) T.` Find the couple acting on the coil when a current of 0.1 A is passed through it and the magnetic field is parallel to its plane. |
|
Answer» Correct Answer - `[8.66 xx 10^(-7)Nm]` |
|
| 38. |
A neutral particle is at rest in a uniform magnetic field `B`. At time `t = 0` it decays into two charged particles, each of mass `m`.(a) If the charge of one of the particles is `+q`, what is the charge of the other?(b) The two particles move off in separate paths, both of them lie in the plane perpendicular to `B`. At a later time, the particles collide. Express the time from decay until collision in terms of `m, B` and `q`. |
|
Answer» Correct Answer - [(a) `-q` (b) `(pi m)/(Bq)` ] |
|
| 39. |
A uniform magnetic field with a slit system as shown in Fig. is to be used as a momentum filter for highenergy charged particles. With a field B tesla, it is found than the filter transmits `alpha` each of energy 5.3MeV. The magnetic field is increased to 2.3 tesla and deuterons are passed into the filter. The energy of each deutrons are passed into the filter. The energy of each deutrons transmitted by the filter is ........... MeV. |
|
Answer» Correct Answer - [14 MeV] |
|
| 40. |
At the moment `t = 0` on electron leaves one plate of a parallel-plate capacitor with a neglible velocity. An accelerting volatage, varrying as `V = at`, where `a = 100 V//s` is applied between the plates is `l = 5.0 cm`. What is the velocity of the of the electron at the moment it reaches the opposite plate? |
|
Answer» Correct Answer - [16 km/s] |
|
| 41. |
Inside a cylindrical capacitor of inner radius a and outer radius b, an electron is projected from the surface of inner cylindrical shell perpendicular to it with an initial velocity. In the annular region between the two cylindrical shells a uniform magnetic induction B exist in direction parallel to the axis of capacitor. Find tbe maximum initial velocity with which tbe electron is to be projected so that it will not hit the outer shell. |
|
Answer» Correct Answer - `[(eB (b^(2) - a^(2)))/(2 mb)]` |
|
| 42. |
A solenod of length 0.4m and diametre 0.6m consists of a single layer of 1000 turns of fine wire carrying a current of `5.0xx10^-3A` . Calculate the magnetic field intensity on the axis at the middle and at the ends of the solenoid. |
|
Answer» Correct Answer - `[2.77pixx10^(-6)T,2pixx10^(-5)T]` |
|
| 43. |
Two straight infinitely long and thin parallel wires are spaced 0.1m apart and carry a current of 10A each. Find the magnetic field at a point distance 0.1m from both wires in the two cases when the currents are in the (a) same and (b) opposite directions. |
|
Answer» Correct Answer - [(a) `3.46 xx 10^(-5)T`; (b) `2 xx 10^(-5)T`] |
|
| 44. |
A capacitor of capacitance C is connected to a battery of EMF E for a long time and then disconnected. The charged capacitor is then connected across a long solenoid having n turns per meter in its closely packed winding on its core. After connections it is found that the voltage across the capacitor drops to `E//eta` in a time `Delta t`. In this period estimate the average magnetic induction at the centre of solenoid. |
|
Answer» Correct Answer - `[(mu_(0)n CE)/(Delta t) (1 - (1)/(eta))]` |
|
| 45. |
A rectangular loop consists of `N = 100` closed wrapped turns and has dimensions `(0.4 m xx 0.3 m)`. The loop is hinged along the y-axis and its plane makes an angle `theta = 30^@` with the x-axis. What is the magnitude of the torque exerted on the loop by a uniform magnetic field `B = 0.8 T` directed along the x-axis when current is `i = 1.2 A` in the direction shown. What is the expected direction of rotation of the loop? |
|
Answer» Correct Answer - `[4.3 xx 10^(-3)Nm]` |
|