Advertisements
Advertisements
Question
Show that Lenz's law is a consequence of conservation of energy.
Advertisements
Solution
According to Lenz law, the polarity of the induced emf is such that it opposes the change in magnetic flux responsible for its production.
Experiment:
When the bar magnet with its N-pole is moved towards the coil, the induced current produced in coil S opposes the motion of magnet. It will happen so, if the induced current in the coil S produces magnetic field lines from left to right i.e., if the induced current flows through the coil S in clockwise direction (when seen from left).
Lenz Law and Principle of Conservation of Energy
Lenz law is in accordance with the law of conservation of energy. In the above experiment, when N-pole of magnet is moved towards the coil, the right face of the coil acquires North polarity. Thus, work has to be done against the force of repulsion in bringing the magnet closer to the coil.
When N pole of magnet is moved away, South pole develops on the right face of the coil. Therefore, work has to be done against the force of attraction in taking the magnet away from the coil.
This mechanical work in moving the magnet with respect to the coil changes into electrical energy producing induced current. Hence, energy transformation takes place. Hence, we can say that Lenz's law is a consequence of conservation of energy.
APPEARS IN
RELATED QUESTIONS
What is the direction of induced currents in metal rings 1 and 2 when current I in the wire is increasing steadily?
Consider the situation shown in figure. If the closed loop is completely enclosed in the circuit containing the switch, the closed loop will show _______________ .
2 A 40 kg boy whose legs are 4 cm in area and 50 cm long falls through a height of 2 m without breaking his leg bones. If the bones can withstand stress of 0.9 x 108 N/m2. The Young's modulus for the material of the bone is ______.
A bar magnet is dropped through a copper ring acceleration of magnet is
For a coil having L = 2 mH, current flows at the rate of 10-3 AIS. The e.m.f induced is
Lenz's law gives ______
Same as problem 4 except the coil A is made to rotate about a vertical axis (figure). No current flows in B if A is at rest. The current in coil A, when the current in B (at t = 0) is counterclockwise and the coil A is as shown at this instant, t = 0, is ______.
A wire in the form of a tightly wound solenoid is connected to a DC source, and carries a current. If the coil is stretched so that there are gaps between successive elements of the spiral coil, will the current increase or decrease? Explain.
Predict the direction of induced current in the situation described by the following figure.
Predict the direction of induced current in the situation described by the following figure.
