Lenz's Law
Interactive Feed
JEE Advanced 1993
LEVELJEE Main
In a straight conducting wire, a constant current is flowing from left to right due to a source of emf. When the source is switched off, the direction of the induced current in the wire will be......
LEVELJEE Main
A current from to is increasing in magnitude. What is the direction of induced current, in the loop as shown in the figure?
LEVELJEE Advanced
The figure shows certain wire segments joined together to form a coplanar loop. The loop is placed in a perpendicular magnetic field in the direction going into the plane of the figure. The magnitude of the field increases with time. and are the currents in the segments and . Then,
(A)
(B)
(C)
is in the direction and is in the direction .
(D)
is in the direction and is in the direction .
LEVELJEE Main
Two identical circular loops of metal wire are lying on a table without touching each other. Loop carries a current which increases with time. In response, the loop
(A)
remains stationary
(B)
is attracted by the loop
(C)
is repelled by the loop
(D)
rotates about its CM, with CM fixed
JEE Advanced 2006
LEVELJEE Main
Comprehension Passage
Modern trains are based on Maglev technology in which trains are magnetically leviated, which runs its EDS Maglev system. There are coils on both sides of wheels. Due to motion of train, current induces in the coil of track which levitate it. This is in accordance with Lenz's law. If trains lower down then due to Lenz's law a repulsive force increases due to which train gets uplifted and if it goes much high, then there is a net downward force due to gravity. The advantage of Maglev train is that there is no friction between the train and the track, thereby reducing power consumption and enabling the train to attain very high speeds.
Disadvantage of Maglev train is that as it slows down the electromagnetic forces decreases and it becomes difficult to keep it leviated and as it moves forward according to Lenz's law, there is an electromagnetic drag force.
Question 1:
What is the advantage of this system ?
(A)
No friction hence no power consumption
(B)
No electric power is used
(C)
Gravitation force is zero
(D)
Electrostatic force draws the train
Question 2:
What is the disadvantage of this system ?
(A)
Train experiences upward force according to Lenz's law
(B)
Friction froce create a drag on the train
(C)
Retardation
(D)
By Lenz's law train experience a drag
Question 3:
Which force causes the train to elevate up ?
(A)
Electrostatic force
(B)
Time varying electric field
(C)
Magnetic force
(D)
Induced electric field
JEE Advanced 1982
LEVELJEE Main
Three identical closed coils , and are placed with their planes parallel to one another. Coils and carry equal currents as shown in figure. Coils and are fixed in position and coil is moved towards with uniform motion. Is there any induced current in ? If no, give reasons. If yes, mark the direction of the induced current in the diagram.
JEE Advanced 2020
LEVELJEE Main
A light disc made of aluminium (a nonmagnetic material) is kept horizontally and is free to rotate about its axis as shown in the figure. A strong magnet is held vertically at a point above the disc away from its axis. On revolving the magnet about the axis of the disc, the disc will (figure is schematic and not drawn to scale)-
(A)
rotate in the direction opposite to the direction of magnet's motion
(B)
rotate in the same direction as the direction of magnet's motion
(C)
not rotate and its temperature will remain unchanged
(D)
not rotate but its temperature will slowly rise
JEE Main 2021
LEVELBoard
A coil is placed in a magnetic field as shown below. A current is induced in the coil because is
(A)
outward and decreasing with time
(B)
parallel to the plane of coil and decreasing with time
(C)
outward and increasing with time
(D)
parallel to the plane of coil and increasing with time