Question
A long, straight wire carries a current. Is Ampere's law valid for a loop that does not enclose the wire? That encloses the wire but is not circular?
✓
Answer
Ampere's law is valid for a loop that is not circular. However, it should have some charge distribution in the area enclosed so as to have a constant electric field in the region and a non-zero magnetic field. Even if the loop defined does not have its own charge distribution but has electric influence of some other charge distribution, it can have some constant magnetic field $\big(\oint\overrightarrow{\text{B}}.\text{d}\overrightarrow{\text{l}}=\mu_0\text{i}\ \text{enclosed}\big).$
Need a full question paper?
Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.
Explore more
Similar questions
A point source emitting light uniformly in all directions is placed 60cm above a table-top. The illuminance at a point on the table-top, directly below the source, is 15 lux. Find the illuminance at a point on the table-top 80cm away from the first point.
The half-life of a radioisotope is 10h. Find the total number of disintegrations in the tenth hour measured from a time when the activity was 1Ci.
- Write three characteristic properties of nuclear force.
- Draw a plot of potential energy of a pair of nucleons as a function of their separation. Write two important conclusions that can be drawn from the graph.
A rod of length L is placed along the X-axis between x = 0 and x = L. The linear density (mass/ length) $\rho$ of the rod varies with the distance x from the origin as $\rho=\text{a + bx.}$
→- Find the SI units of a and b.
- Find the mass of the rod in terms of a, b and L.
A concave mirror of radius R is kept on a horizontal. Water $\big($refractive index $=\mu\big)$ is poured into it upto a height h. Where should an object be placed so that its image is formed on itself?
→If the frequency of light falling on a metal is doubled, what will be the effect on photocurrent and the maximum kinetic energy of emitted photoelectrons?
Find the position of the image formed by the lens combination given in the Fig. $9.20$.
→If the separation between the slits in a Young's double slit experiment is increased, what happens to the fringe-width? If the separation is increased too much, will the fringe pattern remain detectable?
$(a)$ Obtain the expression for the magnetic energy stored in a solenoid in terms of magnetic field $B$, area $A$ and length $l$ of the solenoid. $(b)$ How does this magnetic energy compare with the electrostatic energy stored in a capacitor?
→An object is to be seen through a simple microscope of focal length 12cm. Where should the object be placed so as to produce maximum angular magnification? The least distance for clear vision is 25cm.