A metal “Slinky” can be used as a solenoid. The “Slinky” is stretched slightly, and a current is passed through it. Will the resulting magnetic field cause the “Slinky” to collapse or to stretch out further?
1. collapse
2. stretch out further
3. neither, the magnetic field is zero outside a solenoid
4. the answer depends on the direction of the current
Subtopic:  Force between Current Carrying Wires |
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A conducting wire is bent into the form of a square \(ABCD,\) and electrical connections are established in two different ways:
(I) at two adjacent vertices \(A,B\)
(II) at two points \(A,C\) at the ends of a diagonal.
The same potential difference is established between the two connected ends. Current is, however, allowed to take only a single path from the positive to the negative terminal by disconnecting the other path. Let the magnetic field at the centre in these cases be \(B_\text I,B_\text{II}.\) Then, \(\frac{B_\text I}{B_\text{II}}=\)
1. \(2\) 2. \(\dfrac12\)
3. \(\dfrac{1}{\sqrt2}\) 4. \(1\)
Subtopic:  Magnetic Field due to various cases |
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A wire carrying a current \(I_0\) oriented along the vector \(\big(3\hat{i}+4\hat{j}\big)\) experiences a force per unit length of \(\big(4F\hat{i}-3F\hat{j}-F\hat{k}\big).\) The magnetic field \(\vec{ B}\) equals:

1. \(\dfrac{F}{I_0}\left(\hat{i}+\hat{j}\right)\)

2. \(\dfrac{5F}{I_0}\left(\hat{i}+\hat{j}+\hat{k}\right)\)

3. \(\dfrac{F}{I_0}\left(\hat{i}+\hat{j}+\hat{k}\right)\)

4. \(\dfrac{5F}{I_0}\hat{k}\)

Subtopic:  Lorentz Force |
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To ensure that the magnetic field is radial in a moving coil galvanometer:

1. The number of turns in the coil is increased.
2. The magnet is taken in the form of a horse-shoe.
3. The poles are cut cylindrically.
4. The coil is wound on an aluminum frame.
Subtopic:  Moving Coil Galvanometer |
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A charged particle (charge: \(q\)) moves in a circular orbit in a uniform magnetic field, its orbit enclosing a magnetic flux \(\Phi.\) The angular momentum of the particle is:
 
1. \(q\Phi\) 2. \(\dfrac{q\Phi}{2\pi}\)
3. \(\pi q\Phi\) 4. \(\dfrac{q\Phi}{\pi}\)
Subtopic:  Lorentz Force |
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Given below are two statements: 

Statement I: The magnetic field due to a segment \({d\vec l}\) of a current-carrying wire carrying a current, \(I\) is given by:
  \({d\vec B}=\dfrac{\mu_0}{4\pi}~I\left({d\vec l}\times\dfrac{\vec r}{r^3}\right ),\)
where \(\vec{r}\) is the position vector of the field point with respect to the wire segment.
Statement II: The magnetic field of a current-carrying wire is never parallel to the wire.
 
1. Statement I and Statement II are True and Statement I is the correct explanation of Statement II.
2. Statement I and Statement II are True and Statement I is not the correct explanation of Statement II.
3. Statement I is True, and Statement II is False.
4. Statement I is False, and Statement II is True.
Subtopic:  Biot-Savart Law |
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Two small current-carrying loops carrying currents in the clockwise direction are placed in the same plane, separated by a distance \(d\) (which is much larger than the size of the loops). The two loops:
1. attract each other.
2. repel each other. 
3. exert no force on each other, but exert a torque.
4. neither exert any force nor any torque on each other.
Subtopic:  Current Carrying Loop: Force & Torque |
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Two long straight wires carrying currents \(i_1, i_2\) are placed as shown in the figure, just avoiding contact. The separation between the wires is negligible, and the wires are aligned along \(x\) & \(y\) axes respectively. 
 
The wire along the \(x\text-\)axis experiences:
1. a force along \(+y\) axis only.
2. a force along \(-y\) axis.
3. zero force, but a torque.
4. no force and no torque.
Subtopic:  Force between Current Carrying Wires |
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A metal rod \(PQ\) (carrying current from \(P\) to \(Q\)) is placed perpendicular to an infinitely long wire carrying a current \(i_0.\) If this arrangement lies in a horizontal plane, in which direction will the rod \(PQ\) rotate?

                     
1. clockwise
2. anticlockwise
3. along the axis of \(PQ\)
4. it will not rotate
Subtopic:  Force between Current Carrying Wires |
From NCERT
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A circular coil of radius \(r\) carries a current \(i\) and is placed in a uniform magnetic field \(B,\) with its plane parallel to the field. The magnitude of the torque acting on the coil is:
1. zero 2. \(2\pi r i B\)
3. \(\pi r^2i B\) 4. \(2\pi r^2i B\)
Subtopic:  Current Carrying Loop: Force & Torque |
From NCERT
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