High School Electromagnetic Induction Problems, Urgent !!

The magnitude and direction of the current in the coil m determine the magnitude and direction of the magnetic field generated by the current, and the alternating current shown in Figure (b) will generate an alternating magnetic field with the same change law when the alternating current shown in Figure (b) is passed through the coil. The alternating magnetic field passes through the coil n, and the current will be induced in the ** coil n.

However, the magnitude and direction of the induced current in the n coil are not determined by the magnitude and direction of the magnetic flux passing through it, but by the speed and direction of the change of the magnetic flux through it, that is, the magnitude and direction of the rate of change of the magnetic flux, and the change of this magnetic flux is determined by the speed and direction of the current change in the coil m. From this, it can be seen that at 0, t2, t4 ...At the same time, the current changes the fastest in coil m, 0, t3....and t2, t5....in opposite directions; And at T1, T3....The rate of change of the current at the same time is zero. From the above analysis, it can be seen that at 0, t2, t4....The induced current in coil n is the largest at equal time, at T1, T3....The current is zero at the same time.

By comparing the current of the M and N coils, you can determine the magnitude of the interaction force between the M and N coils and whether they attract or repuls.

As can be seen from the two diagrams, at time T1, the induced current in coil n is zero; And at time T2, the current in coil m is zero. Thus the interaction force must be zero at these two moments. Options A and B can be excluded first.

And because the parallel currents in the same direction attract each other, and the parallel currents in the opposite direction repel each other, during the time from T1 to T2, the current direction is the same, and it should be attracted to each other, and option c can be excluded. Obviously, option d is correct.

Choose b, dThe greater the rate of change of the alternating current, that is, the greater the derivative of the image, the greater the effect of the force between the currents generated in the B-coil that resists the change of the original magnetic field.

Analysis: The conductor rod cuts the magnetic inductance line to produce an induced electromotive force, and its magnitude is E=BLV, where B and L remain unchanged, and the velocity V gradually increases, so E becomes larger, so option A is wrong; The conductor rod is equivalent to the power supply part of the closed circuit, because the electromotive force E becomes larger, the current flowing through the bulb L becomes larger, the bulb becomes brighter, and option B is wrong;

If the direction of the magnetic field is perpendicular to the plane, then the direction of the current flowing through the conductor rod is from bottom to top, that is, the upper potential of the conductor rod is high, and the upper plate of the capacitor is positively charged, option c is wrong; Anyway, if the direction of the magnetic field is perpendicular to the plane outward, the same can be seen that option c is correct;

Because the electromotive force e in the circuit becomes larger, the potential difference u between the two plates of the capacitor becomes larger, and according to e=u d, the electric field strength increases, and option d is correct.

To sum up, the answer to this question is cd (when the magnetic field is outward) or d (when the magnetic field is inward).

D, a induces the electric banquet momentum to increase, c the upper plate is positively charged, and the brightness of b bulb increases. e=b*l*v, accelerate the movement, the electromotive force induced by the good Wang increases, the socks are continuously charged, the voltage between the plates gradually increases, and the electric field strength increases.

Is the change in magnetic flux a sine or a cosine change? Answer: Sinusoidal change. Because the higher the current, the greater the magnetic flux generated.

Is the rate of change of magnetic flux a sine or a cosine change? Answer: Cosine variation.

Because the rate of change of the magnetic flux is equal to the rate of change of the electric current, and the rate of change is equal to the tangent of the tangent. As can be seen from the graph, the rate of change of the current is the largest at t=0, so the rate of change of the magnetic flux is also the largest. The rest is the same, so it can be seen that the rate of change of the magnetic flux is the cosine change.

Why is the force zero when the current is at its maximum? Answer, because the magnitude of the induced electromotive force is determined by the rate of change of the magnetic flux, the greater the rate of change, the greater the induced electromotive force, and when the current is maximum, its rate of change is zero, so the rate of change of the magnetic flux is also zero. Therefore, the B coil does not induce electromotive force, so there is no current, and one coil has current, and the other has no current, how can there be interaction force.

So the force is zero.

Let the length of AB be L, the magnetic induction intensity be B, and the resistance is obtained by the induced electromotive force in the circuit E=BLVAB and the induced current in the circuit is I=E (R 2), and the ampere force of AB F=Bil=2B 2L 2 3R2 The thermal power consumed by the resistance R1 P1=(12I)2R=B2L2V29R

by , p1=fv6

c f=un=umgcos p2=fv d The mechanical power consumed by the whole device is p3=fv+p2=(f+ mgcos)v

When passing through a magnetic field, the frictional force is converted into internal energy by negative work, and the gravitational force and ampere force are also negative work and converted into internal energy and electrical energy. Is it okay?

The direction of the induced current generated in AB is from A to B. The direction of the ampere force is upwards along the inclined plane.

If the current is constantly increasing, then the metal rod should slide upwards and the friction will first decrease downwards and then increase upwards. (Seems to pick D).

However, the condition in the problem is that b0 increases uniformly, the induced electromotive force in the closed loop should be constant, the current should be constant, and the frictional force should be constant. From this, it can be said that there is a problem with the design of the topic.

If the B0 acceleration increases, then choosing D is fine.

I hope it will be helpful to you, please adopt it in time. If you have any questions, we are here to help. Good luck with your studies!

Answer: D decreases first and then increases.

When t=0, f=mgsina b0 increases uniformly, and the induced current is from a to b ampere force along the inclined plane. The friction decreases to zero and then increases downwards.

Choose D1In the initial state, when the frictional force is upward, and the component of gravity begins to increase, according to the principle of increase, inverse and subtraction, the force ab is changed, and the frictional force and ampere force are upward to reduce the area, and at this time, the two forces are superimposed to cancel the gravitational force, and the motion has not yet begun.

3.When the equilibrium limit is reached, the ampere force balances the frictional force (at this point, the frictional force has reversed, downward) and the gravitational force starts to move after which the frictional force does not change o t time period which belongs to the above 2 phases.

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Example 1] (2004, Shanghai Comprehensive) The basic principle of power generation is electromagnetic induction. The scientist who discovered the phenomenon of electromagnetic induction is ().

a Amp B Hertz.

c Faraday D Maxwell.

Analysis: This question tests the knowledge about the history of physics, and you should know that Faraday discovered the phenomenon of electromagnetic induction.

Answer: C Example 2] The scientist who discovered the phenomenon of the magnetic effect of electric current is The scientist who discovered the law of the force of an energized wire in a magnetic field is The scientist who discovered the phenomenon of electromagnetic induction is the scientist who discovered the law of the interaction force between electric charges

Analysis: This question tests knowledge about the history of physics.

Answer: Oster Ampere Faraday Coulomb.

Understanding of concepts and awareness of physical phenomena.

Example 3] Among the following phenomena, the phenomenon of electromagnetic induction is ()a: the effect of a magnetic field on the force generated by an electric current.

b The varying magnetic field causes an electric current to be generated in the closed circuit.

c A soft iron rod inserted in an energized solenoid is magnetized.

d A magnetic field is generated around the electric current.

Analysis: The phenomenon of electromagnetic induction refers to the phenomenon of generating an electric current in a magnetic field, and option B is correct.

Answer: b Consolidation exercises.

1.Regarding magnetic flux, magnetic flux density, magnetic induction intensity, the following statements are true ()a The greater the magnetic induction intensity, the greater the magnetic flux.

b When the magnetic flux passing through a coil is zero, the magnetic flux density is zero c The greater the magnetic flux density, the greater the magnetic induction intensity.

d Analysis of the maximum magnetic flux traversed by the magnetic induction intensity on an area numerically equal to 1 m2: b The reason for "the magnetic flux is zero" in the answer b may be that the magnetic induction intensity (magnetic flux density) is zero, or it may be that the coil plane is parallel to the magnetic induction intensity. Answer:

Answer: According to the kinematic formula, the speed at which the metal rod cuts the magnetic inductance line is the solution of the knowing option (c answer.

Find a short section above, (micro-element method) can judge that the upper part of the force perpendicular paper faces inward, and the lower part of the force perpendicular paper faces outward, so it will be wound around the magnet, and from the top down, it is counterclockwise, so the magnetic field of the current is the same as the direction of the bar magnetic field.

The force on the top is inward, and the force on the bottom is outward, so choose C

A, explanation: because of the sliding rheostat, the magnetic field induced by the sliding rheostat is also changed, and Ab is set on the core, the situation of the two is the same, the change of magnetic flux will produce current, so Ab has a current, and the magnetic flux of C is always O, because the magnetic field direction of the upper and lower core forces is opposite, it is canceled.

When the speed of AB sliding reaches stability, the ampere force is equal to the component force of gravity along the metal guide rail surface, and we can get: B i L = mg sin, and we can get: I = mg sin BL = 3 10 -2 10 A = A

by e = b l v and i = e (r + r).

You can get : v = i (r + r) bl = (m s = 10 m s

The voltage of capacitor c is equal to the voltage across the r, which is u = i r = v = v

Capacitor c: The amount of charge of a plate strip q = cu = 10 10 -6 c = c

From the right-hand rule, it can be seen that the current in AB flows from B to A, so the plate connected to the capacitor C and the A terminal is positively charged.

That is, the amount of charge carried by the plate connected to the capacitor C and the A terminal is + C