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%
From NCERT

To unlock all the explanations of this course, you need to be enrolled.

Hints

To unlock all the explanations of this course, you need to be enrolled.


Identical cells are connected to identical square wire loops as shown in the two diagrams, and the magnetic fields are respectively \(B_1\) and \(B_2\) at the centres. 

Then, we can conclude that:
1. \(B_1>0, B_2=0\)
2. \(B_1> B_2>0\)
3. \(B_2> B_1>0\)
4. \(B_1=0, B_2=0\)
Subtopic:  Biot-Savart Law |
 57%
From NCERT

To unlock all the explanations of this course, you need to be enrolled.

Hints

To unlock all the explanations of this course, you need to be enrolled.


An \(\alpha\)-particle and a proton of the same kinetic energy move along circular paths of radii \(r_{\alpha}\) and \(r_p\) respectively, in the same magnetic field. The ratio \((r_{\alpha} / r_p) \) equals: 
1. \(2\) 2. \( \dfrac{1} {2}\)
3. \(1\) 4. \(4\)
Subtopic:  Lorentz Force |
 65%
From NCERT

To unlock all the explanations of this course, you need to be enrolled.

Hints

To unlock all the explanations of this course, you need to be enrolled.


advertisementadvertisement

A particle of mass \(m\) and the charge \(q\) is observed to move with a uniform velocity \(v\) in a region containing a uniform magnetic field \(B,\) and a uniform gravitational field \(g.\) The magnetic field \(B\) must satisfy:
1. \(B = \dfrac{mg}{qv}\)

2. \(B \leq \dfrac{m g}{q v}\)

3. \(B \geq \dfrac{m g}{q v}\)

4. \(B = \dfrac{qv}{mg}\)
Subtopic:  Lorentz Force |
From NCERT

To unlock all the explanations of this course, you need to be enrolled.

Hints

To unlock all the explanations of this course, you need to be enrolled.


A straight long current-carrying wire carrying a current \(i\) is placed in a uniform magnetic field, and it is observed that the field vanishes at a point which is at a distance \(r\) from the wire. The force on the wire, per unit length, is:
1. \(\dfrac{\mu_{0} i^{2}}{2 \pi r}\) 2. \(\dfrac{\mu_{0} i^{2}}{4 \pi r}\)
3. \(\dfrac{\sqrt{2} \mu_{0} i^{2}}{2 \pi r}\) 4. \( \dfrac{\mu_{0} r^{2}}{2 \pi r \sqrt{2}}\)
Subtopic:  Force between Current Carrying Wires |
 76%
From NCERT

To unlock all the explanations of this course, you need to be enrolled.

Hints

To unlock all the explanations of this course, you need to be enrolled.


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 |
From NCERT

To unlock all the explanations of this course, you need to be enrolled.

Hints

To unlock all the explanations of this course, you need to be enrolled.


advertisementadvertisement

A current \(i\) is distributed uniformly over the cross-section of a cylindrical wire of radius \(R,\) as shown in the diagram. The magnetic field at the surface is \(B_s.\) The magnetic field at the point \(P\) inside the cross-section equals: \(\left(OP =\dfrac{R}{2}\right )\)
1. \(\dfrac{B_s}{2}\) 2. \(2 B_s\)
3. \(\dfrac{B_s}{4}\) 4. \(4 B_s\)
Subtopic:  Ampere Circuital Law |
 57%
From NCERT

To unlock all the explanations of this course, you need to be enrolled.

Hints

To unlock all the explanations of this course, you need to be enrolled.


Two semi-circular current-carrying wires are placed in the same plane so that they share a common centre. The magnetic field due to any one of them at the common centre has the magnitude, \(B_O\). When one of them is tilted so that it is in a perpendicular plane, with the same centre, the magnetic field at the common centre is \(B\). Then,
1. \(B =2B_O\)
2. \(B~=\dfrac{B_O}{2}\)
3. \(B=\sqrt 2 B_O\)
4. \(B=\dfrac{B_O}{\sqrt 2}\)
Subtopic:  Magnetic Field due to various cases |
 74%
From NCERT

To unlock all the explanations of this course, you need to be enrolled.

Hints

To unlock all the explanations of this course, you need to be enrolled.


A straight current-carrying wire carrying current \(I\) passes perpendicular to the plane of an imaginary rectangular loop \(PQRS\), passing through its centre \(O\) (into the diagram). The diagonals intersect at \(60^\circ,\) and side \(PS\) is smaller than side \(PQ\). The value of \(\int \vec{B} \cdot d\vec{l}\) evaluated from \(P\) to \(Q\) (along \(PQ\)) has the magnitude:
1. \(\dfrac{\mu_{0} I}{6}\) 2. \(\dfrac{2 \mu_{0} I}{6}\)
3. \(\dfrac{4\mu_{0} I}{6}\) 4. \(\dfrac{5\mu_{0} I}{6}\)
Subtopic:  Ampere Circuital Law |
 52%
From NCERT

To unlock all the explanations of this course, you need to be enrolled.

Hints

To unlock all the explanations of this course, you need to be enrolled.


advertisementadvertisement

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 |
From NCERT

To unlock all the explanations of this course, you need to be enrolled.

Hints

To unlock all the explanations of this course, you need to be enrolled.