LENZ\'S LAW: Lenz\'s law will allow you to figure out the directionof induced cu

Question

LENZ'S LAW: Lenz's law will allow you to figure out the directionof induced current flow due to a changing magnetic field. If theapplied
magnetic field is increasing in a loop, Lenz's law tells us thatthe induced current will be such that it will produce an inducedmagnetic field that will cancel out the increase in the appliedmagnetic field. Conversely, if the applied field is decreasing, theinduced current will be in a direction that induces a magneticfield that will cancel out the decrease in the applied magneticfield. In other words, nature wants the field to remain constant.You can determine the required direction of the current by usingthe right hand rule as discussed in the previous lab.

Answer:

Answer:  

3. The lab manual discusses the effect ofplacing a metal rod into the inner coil. What effect do you expectthis to have on the induced current in the outer coil when theapplied current in the inner coil changes?

mark the right answer

A) The induced current will be smaller than without the metalrod.
B) The induced current will be larger than without the metalrod.
C) The induced current will be the same as without the metalrod.
D) The induced current will be in the opposite direction than thecase without the metal rod.

Answer:

Faraday's law of induction tells us that the magnitude of aninduced EMF (voltage) is equal to the rate of change ofthe magnetic flux through the loop:?= - dphi/dt. As the flux changes with time, an induced voltage will be producedthat creates a current in the loop. In the above expression, phi is the flux through the loop. For a field that is perpendicular tothe face of the loop, it is given by phi=BA, where B is the magnetic field and A is the areaof the loop. Obviously, the more rapid the change in B,and therefore phi, the larger the induced EMF. Note thatif you have more than one loop (a coil), then Faraday's law ismodified by multiplying by the number of turns in the coil, . LENZ'S LAW: Lenz's law will allow you to figure out the directionof induced current flow due to a changing magnetic field. If theapplied magnetic field is increasing in a loop, Lenz's law tells us thatthe induced current will be such that it will produce an inducedmagnetic field that will cancel out the increase in the appliedmagnetic field. Conversely, if the applied field is decreasing, theinduced current will be in a direction that induces a magneticfield that will cancel out the decrease in the applied magneticfield. In other words, nature wants the field to remain constant.You can determine the required direction of the current by usingthe right hand rule as discussed in the previous lab. 1. Thinking about Faraday's law, consider what happens as you pushthe north pole of a magnet into a coil. In which case do you expectthe induced current in the coil to be the greatest? mark the right answer A) When the magnet is stationary within the coil. B) At the moment before the magnet is pushed into the coil. C) When the magnet is pushed into the coil rapidly. D) When the magnet is pushed into the coil slowly. 2) Now let's consider the case where you have one coil insideanother. In which case will the induced current in the outer coil be the largest? mark the right answer A) When the applied current in the inner coil isincreased slowly. B) When the applied current in the inner coil is increasingrapidly. C) When the applied current in the inner coil is constant. D) When there is no applied current in the inner coil. 3. The lab manual discusses the effect ofplacing a metal rod into the inner coil. What effect do you expectthis to have on the induced current in the outer coil when theapplied current in the inner coil changes? mark the right answer A) The induced current will be smaller than without the metalrod. B) The induced current will be larger than without the metalrod. C) The induced current will be the same as without the metalrod. D) The induced current will be in the opposite direction than thecase without the metal rod. A loop is placed in a magnetic field as shown in the figure. If themagnitude of the field is increased, the induced current in theloop will be mark the right answer A) into the page. B) out of the page. C) counter clockwise. D) clockwise.

Explanation / Answer

1.When a magnet is moved toward the loop,the reading of theammeter changes from zero in one direction.When the magnet isbrought to rest and held stationary relative to the loop,a readingof zero is observed.When the magnet is moved away from the loop,thereading on the ammeter changes in the oppositedirection.Finally,when the magnet is held stationary and the loopis moved either toward or away from it,the reading changes fromzero.Therefore,the induced current in the coil is greatest when themagnet is pushed into the coil rapidly. 2.When one coil is inside another the induced current in theouter coil will be the greatest when the applied current in theinner coil is increasing rapidly.This is because when the appliedcurrent in the inner coil is increasing rapidly,then the magneticflux linked with the outer coil changes rapidly.Hence the inducedcurrent in the outer coil is the greatest. 3.When a metal rod is placed inside the inner coil,themagnetic flux linked with the outer coil decreases.As the magneticflux linked with the outer coil decreases,therefore,the inducedcurrent will be larger than without the metal rod. 4.The magnetic field is directed into the plane of theloop.Therefore,according to Ampere's right hand thumb rule theinduced current in the loop will be counter clockwise.According toAmpere's right hand thumb rule when the thumb of the right handpoints in the direction of the current flow then the curling offingers of the right hand gives the direction of the magneticfield.Therefore,when the magnitude of the field is increased, theinduced current in the loop will be counter clockwise.

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