The voltmeter consists of a \(50~\Omega\) coil which gives full-scale deflection when a current of \(10\) mA flows through it, and a resistor of \(950~\Omega\) connected with it. The reading of the voltmeter is:

                                
1. \(9~\text{V}\)
2. \(8.8~\text{V}\)
3. \(8~\text{V}\)
4. \(10~\text{V}\)

Subtopic:  Conversion to Ammeter & Voltmeter |
 50%
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A circular wire carrying current \(I\) produce the same magnetic field at its centre as an infinite straight wire carrying the same current \((I)\) does, at a distance \(d\). The radius of the circular wire is:

1. \(\dfrac{d}{2\pi}\) 2. \(\dfrac{d}{\pi}\)
3. \(2\pi d\) 4. \(\pi d\)
Subtopic:  Magnetic Field due to various cases |
 82%
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A particle of mass \(m\), charge \(q\) enters a region where there is a uniform magnetic field \(B\), its initial motion being perpendicular to the field. Along the direction of the magnetic field, there is also an electric field \(E\), which is uniform. By the time the particle has turned through a "full circle" in the plane perpendicular to \(B\), its speed doubled. The initial speed is:

1. \(\dfrac{E}{B}\)
2. \(\dfrac{2 \pi E}{B}\)
3. \(\dfrac{2 \pi \sqrt{3} E}{B}\)
4. \(\dfrac{2 \pi E}{\sqrt{3} B}\)
Subtopic:  Lorentz Force |
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Two insulated current carrying wires lie along the \(x\) and the \(y\text-\)axis in the \(xy\text-\)plane, carrying identical currents \(I\). The magnetic field at the point \((d,-d)\) is:

1. \(\text{Zero}\) 2. \(\dfrac{\mu_0I}{\pi d}\)
3. \(\sqrt2\cdot \dfrac{\mu_0I}{2\pi d}\) 4. \(\dfrac{\mu_0I}{2\pi (\sqrt2 d)}\)
Subtopic:  Magnetic Field due to various cases |
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A current-carrying loop of wire in the shape of a square of side \(a\) lies in the \(x\text-y\) plane. A uniform magnetic field \(B\) acts in the plane. Then:
                      
1. The force on the loop is \(4iaB\).
2. The torque on the loop is \(ia^2B\).
3. The force on the loop is \(\sqrt {2} iaB\).
4. The torque on the loop is \(\sqrt{2}ia^2B\).
Subtopic:  Lorentz Force |
 62%
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Two long parallel wires carry currents, equal to \(i\) each, in opposite directions. The distance between the wires is \(d\). The net magnetic field, at a point which is at an equal distance \(d\) from each of the wires, is:
1. \(\dfrac{\mu_{0} i}{2 \pi d}\) 2. \(\dfrac{2\mu_{0} i}{2 \pi d}\)
3. \(\dfrac{\sqrt 3\mu_{0} i}{2 \pi d}\) 4. zero
Subtopic:  Magnetic Field due to various cases |
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When a particle of charge \(q\) and mass \(m\) is projected perpendicular to a magnetic field, it moves in a circle of radius \(r.\) When the particle is projected upward with the same kinetic energy in a uniform gravitational field \((g)\), it rises to a height \(h\). The magnetic field is:

1. \(\dfrac{m}{q r} \sqrt{\dfrac{g h}{2}}\) 2. \(\dfrac{2m}{q r} \sqrt{\dfrac{g h}{2}}\)
3. \(\dfrac{m}{2q r} \sqrt{\dfrac{g h}{2}}\) 4. none of the above.
Subtopic:  Lorentz Force |
 73%
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A long solenoid has a square cross-section of side \(a\). It has turn-density n (number of turns per unit axial length). A current \(i\) is passed through this solenoid. The magnetic field at the centre of the solenoid is \(B_c\). Then, \(B_c\) is proportional to:
(I) \(a\)
(II) \( \dfrac{1} {a}\)
(III) \(n\)
(IV) \(i\)
Choose the correct option from the given ones:
1. I, III, IV 
2. II, III, IV 
3. III, IV
4. IV Only 
Subtopic:  Magnetic Field due to various cases |
 73%
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Two current carrying loops of wire are placed as shown in the figure, the inner loop \((P)\) having a radius \((r)\) which is much smaller than the radius \((R)\) of the outer loop \((Q)\). Both the loops are concentric, but the currents in one case are in the same sense while in the other, in the opposite sense.

In both cases, the torque on \(P\) due to \(Q\) is zero. If \(P\) is slightly rotated about a diameter, then, it will return to its initial position in:
1. case (I) but not in case (II).
2. case (II) but not in case (I).
3. both cases (I) and (II).
4. neither of cases (I) and (II).
Subtopic:  Magnetic Moment |
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Two very long wires of length \(L\) are placed parallel to each other separated by a distance \(r(r << L)\). The wires carry equal currents \(i\). The force between the two wires is nearly:
1. \(\dfrac{\mu_{0} i^{2} L}{2 \pi r}\) 2. \(\dfrac{\mu_{0} i^{2} L}{4 \pi r}\)
3. \(\dfrac{\mu_{0} i^{2} L}{2 r}\) 4. \(\dfrac{\mu_{0} i^{2} L}{4 r}\)
Subtopic:  Force between Current Carrying Wires |
 83%
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