\(\mathrm{C}\) and \(\mathrm{Si}\) both have the same lattice structure, having \(4\) bonding electrons in each. However, \(\mathrm{C}\) is an insulator whereas \(\mathrm{Si}\) is an intrinsic semiconductor. This is because:
1. in the case of \(\mathrm{C},\) the valence band is not completely filled at absolute zero temperature.
2. in the case of \(\mathrm{C},\) the conduction band is partly filled even at absolute zero temperature.
3. the four bonding electrons in the case of \(\mathrm{C}\) lie in the second orbit, whereas in the case of \(\mathrm{Si},\) they lie in the third.
4. the four bonding electrons in the case of \(\mathrm{C}\) lie in the third orbit, whereas for \(\mathrm{Si},\) they lie in the fourth orbit.
Subtopic:  Energy Band theory |
 72%
Level 2: 60%+
NEET - 2012
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The height at which the weight of a body becomes \(\left ( \frac{1}{16} \right )^\mathrm{th}\) of its weight on the surface of the earth (radius \(R\)) is:
1. \(5R\)
2. \(15R\)
3. \(3R\)
4. \(4R\)

Subtopic:  Acceleration due to Gravity |
 79%
Level 2: 60%+
AIPMT - 2012
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An electron of a stationary hydrogen atom passes from the fifth energy level to the ground level. The velocity that the atom acquired as a result of photon emission will be:
(\(m\) is the mass of hydrogen atom, \(R\) is Rydberg constant and \(h\) is Plank’s constant)
1. \(\dfrac{24m}{25hR}\) 2. \(\dfrac{25hR}{24m}\)
3. \(\dfrac{25m}{24hR}\) 4. \(\dfrac{24hR}{25m}\)
Subtopic:  Bohr's Model of Atom |
 62%
Level 2: 60%+
AIPMT - 2012
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A compass needle which is allowed to move in a horizontal plane is taken to a geomagnetic pole. It:

1. will become rigid showing no movement

2. will stay in any position

3. will stay in north-south direction only

4. will stay in east-west direction only

Level 3: 35%-60%
AIPMT - 2012
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In the circuit shown cells, \(A\) and \(B\) have negligible resistance. For \(V_A =12 ~\text{V},\) \(R_1 = 500 ~\Omega ,\) and \(R = 100 ~\Omega ,\) the galvanometer \((\text{G}) \) shows no deflection. The value of \(V_B\) is: 

1. \(4~\text V\) 2. \(2~\text V\)
3. \(12~\text V\) 4. \(6~\text V\)
Subtopic:  Kirchoff's Voltage Law |
 77%
Level 2: 60%+
AIPMT - 2012
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Four-point charges \(-Q, -q,~ 2q~\text{and}~2Q \) are placed, one at each corner of the square. The relation between \(Q\) and \(q\) for which the potential at the center of the square is zero is:
1. \(Q= -q\)
2. \(Q= -2q\)
3. \(Q= q\)
4. \(Q= 2q\)

Subtopic:  Electric Potential |
 78%
Level 2: 60%+
AIPMT - 2012
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A car of mass \(1000\) kg negotiates a banked curve of radius \(90\) m on a frictionless road. If the banking angle is of \(45^\circ,\) the speed of the car is:

1. \(20\) ms–1 2. \(30\) ms–1
3. \(5\) ms–1 4. \(10\) ms–1
Subtopic:  Banking of Roads |
 90%
Level 1: 80%+
AIPMT - 2012
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A solid cylinder of mass \(3\) kg is rolling on a horizontal surface with a velocity of \(4\) ms-1. It collides with a horizontal spring of force constant \(200\) Nm-1. The maximum compression produced in the spring will be:
1. \(0.5\) m
2. \(0.6\) m
3. \(0.7\) m
4. \(0.2\) m

 63%
Level 2: 60%+
AIPMT - 2012
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One mole of an ideal gas goes from an initial state \(A\) to the final state \(B\) with two processes. It first undergoes isothermal expansion from volume \(V\) to \(3V\) and then its volume is reduced from \(3V\) to \(V\) at constant pressure. The correct \((P-V)\) diagram representing the two processes is:

1. 2.
3. 4.
Subtopic:  Types of Processes |
 82%
Level 1: 80%+
AIPMT - 2012
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Two spheres \(A\) and \(B\) of masses \(m_1\) and \(m_2,\) respectively, collide. \(A\) is at rest initially and \(B\) is moving with velocity \(v\) along the \(x\text-\)axis. After the collision, \(B\) has a velocity \(\frac{v}{2}\) in a direction perpendicular to the original direction. The mass \(A\) moves after collision in the direction:
1. same as that of \(B.\)
2. opposite to that of \(B.\)
3. \(\theta = \text{tan}^{-1}\left(\frac{1}{2} \right)\) to the positive \(x\)-axis.
4. \(\theta = \text{tan}^{-1}\left(\frac{-1}{2} \right )\) to the positive \(x\)-axis.
Subtopic:  Collisions |
Level 3: 35%-60%
AIPMT - 2012
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