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
Figure shows two blocks of masses m and M connected by a string passing over a pulley. The horizontal table over which the mass m slides is smooth. The pulley has a radius r and moment of inertia I about its axis and it can freely rotate about this axis. Find the acceleration of the mass M assuming that the string does not slip on the pulley.
Consider the situation shown in figure. What are the signs of q1 and q2? If the lines are drawn in proportion to the charge, what is the ratio $\frac{\text{q}_1}{\text{q}_2}?$
→
The velocity-time graph of a particle in one-dimensional motion is shown in:
Which of the following formulae are correct for describing the motion of the particle over the time-interval t1 to t2:
-
x(t2) = x(t1) + v(t1) (t2 – t1) + (1/2) a(t2 – t1)2
-
v(t2) = v(t1) + a(t2 – t1)
-
vaverage = (x(t2) –x(t1))/(t2 – t1)
-
aaverage = (v(t2) –v(t1))/(t2 – t1)
-
x(t2) = x(t1) + vaverage (t2 – t1) + (1/2) aaverage (t2 – t1)2
-
x(t2) – x(t1) = area under the v-t curve bounded by the t-axis and the dotted line shown.
According to the station clocks, two babies are born at the same instant, one in Howrah and other in Delhi.
- Who is elder in the frame of 2301 Up Rajdhani Express going from Howrah to Delhi?
- Who is elder in the frame of 2302 Dn Rajdhani Express going from Delhi to Howrah.
A converging lens and a diverging mirror are placed at a separation of 15cm. The focal length of the lens is 25cm and that of the mirror is 40cm. Where should a point source be placed between the lens and the mirror so that the light, after getting reflected by the mirror and then getting transmitted by the lens, comes out parallel to the principal axis?
Plot the corresponding reference circle for each of the following simple harmonic motions. Indicate the initial (t = 0) position of the particle, the radius of the circle, and the angular speed of the rotating particle. For simplicity, the sense of rotation may be fixed to be anticlockwise in every case: (x is in cm and t is in s).
→$\text{x}=2\cos\pi\text{t}$
What is the position at any time, for a body starting from rest, with an acceleration a = at2?
Explain the pressure exerted by an ideal gas and also find the average kinetic energy per molecule of the gas.
One mole of an ideal gas is taken in a Carnot engine working between 27°C and 227°C. The useful work done in one cycle is 600J. Calculate the ratio of the volume of the gas at the end and beginning of the isothermal expansion. Given R = 8.31J mole-1 K-1.
The electric field associated with a monochromatic beam becomes zero 1.2 × 1015 times per second. Find the maximum kinetic energy of the photoelectrons when this light falls on a metal surface whose work function is 2.0eV.