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(SOLVED)
Note : All Answers are in red.
1. Which of the following form (s) a virtual and erect image for all positions of a real object?
Convex lens
Concave lens
Convex mirror
Concave mirror
2. A coil having N turns is wound tightly in the form of a spiral with inner and outer radii a and b respectively. When a current I passes through the coil, the magnetic field at the centre is
- Ans
3. The magnetic field lines due to a bar magnet are correctly shown in:
- Ans
4. A particle of mass ` m ` and charge ` q ` moves with a constant velocity ` v ` along the positive x direction. It enters a region containing a uniform magnetic field B directed along the negative z direction, extending from x = a to x = b. The minimum value of v required so that the particle can just enter the region x > b is:
- Ans
5. A long straight wire along the z - axis carries a current I in the negative z direction. The magnetic vector field B at a point having coordinates (x, y) in the z = 0 plane is:
- Ans
6. A current carrying loop is placed in a uniform magnetic field towards right in four different orientations, I, II, III & IV, arrange them in the decreasing order of Potential Energy.
(i) 
(ii) 
(iii) 
(iv) 
I, III, II, IV
I, II, III, IV
I, IV, II, III
III, IV, I, II
7. The drift velocity of electrons in a conducting wire is of the order of 1mm/s, yet the bulb glows very quickly after the switch is put on because
the random speed of electrons is very high, of the order of 106 m/s
the electrons transfer their energy very quickly through collisions
electric field is set up in the wire very quickly, producing a current through each cross section, almost intantaneousty
All of above
8. In the presence of an applied electric field (
) in a metallic conductor.
The electrons move in the direction of
The electrons move in a direction opposite to
The electrons may move in any direction randomly, but slowly drift in the direction of .
The electrons move randomly but slowly drift in a direction opposite to .
9. Read the following statements carefully : Y: The resistivity of a semiconductor decreases with increase of temperature Z : In a conducting solid, the rate of collisions between free electrons and ions increases with increase of temperature Z : Select the correct statement from the following
Y is true but Z is false
Y is false but Z is true
Both Y and Z are true
Y is true and Z is the correct reason for Y
10. Electrons are emitted by a hot filament and are accelerated by an electric field as shown in fig. The two stops at the left ensure that the electron beam has a uniform cross-section.
The speed of the electron is more at B than at A.
The electric current is from left to right
The magnitude of the current is larger at B than at A.
The current density is more at B than at A.
