Experiments of Faraday and Henry

What was Experiment 1 of Faraday and Henry?

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In the first experiment of Faraday and Henry, a coil was connected to a galvanometer. Then a bar magnet was pushed towards the coil This was done in a way that the north pole was pointing towards the coil. It was noticed that as the bar magnet shifted, the galvanometer showcased deflection. The same thing was done with the South Pole.

It was observed in this experiment of Faraday and Henry that the shift and deflection took place only when the magnet was in motion and not when it was stationary. The point of deflection is small or large depending on the speed at which the motion takes place.

The conclusion of the Faraday and Henry experiment was that there was relative motion between the coil and magnet, resulting in the generation of current in the coil.

What was the Second Experiment of Faraday and Henry?

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In this experiment, the bar magnet of the circuit was replaced with another coil that had current generated within it that was connected to a battery. The current coil which was connected to a battery produces a steady current. The second coil that was the primary coil shows deflection in the galvanometer pointer, which indicates the presence of current in it.

Here, same as above, the degree to which the deflection took place depended on the motion of the secondary coil towards the primary coil. The magnitude also depends on the speed with which it was moved. This shows how the second case is analogous to the first.

What was the Third Experiment of Faraday and Henry?

Faraday concluded from the above two experiments that the relative motion between the magnet and the coil resulted in the current generation in the primary coil. However, another experiment by Faraday showed that relative motion between the coils was not necessary for the primary current to be generated. 

He used two stationary coils in this experiment, one connected to the galvanometer and the other to a battery via a push-button. The galvanometer in the other coil deflected as the button was pressed, showing the presence of current in that coil. Furthermore, the deflection in the pointer was only temporary; if the key was pinned down indefinitely, the pointer indicated no deflection, and when the key was released, the deflection reversed.

However, the third experiment of Faraday and Henry showcases that the relative motion is not necessary to produce current. Both of the coils are steadily placed, one is connected to the battery and the other to a galvanometer. The button in the battery when pushed repeatedly does not pass current but when pushed once, the galvanometer deflects.

Hopefully, some concepts of the experiment by Faraday and Henry are clear.

Solved Examples

1. What was not included in experiment 1 of Faraday and Henry?

1. Galvanometer

2. Coils

3. Funnel

4. Battery

Ans: Funnel. There was no funnel in experiment 1 of Faraday and Henry.

2. Find the true statement.

a) The current in the primary did not have to be generated by relative motion between the coils.

b) In the second experiment, the direction of deflection of the pointer is unaffected by the direction of motion of the secondary coil towards or away from the primary coil.

c) The deflections in the galvanometer are the same when the south pole of the bar magnet is moved towards or away from the coil for similar motions as the north pole.

d) When the bar magnet is maintained stationary while the coil is in motion, the effect is different.

Ans: Option d. Is correct. The current in the primary was generated even without relative motion between the coils. In the third experiment, Faraday used two stationary coils and used a push-button to link one to the galvanometer and the other to a battery. The galvanometer in the other coil deflected as the button was pressed, indicating the presence of current in that coil. All the other statements are false.

3. Which of the following factors affects the galvanometer's deflection?

a) Area of the coil

b) Current passing through the coil

c) Speed with which the bar magnet is dragged toward or away from the coil

d) Resistance offered for current flow

Ans: Option c is correct. The speed with which the bar magnet is dragged towards or away from the coil determines the size of the deflection of the pointer. In addition, the direction of deflection of the pointer is determined by the motion of the bar magnet.

4. Faraday and Henry’s third experiment shows that:

1. Electric current must always be induced by relative motion between the two coils.

2. The relative motion of the two coils is not required to generate an electric current.

3. When the iron rod is placed axially into the coils, the induced current decreases.

4. None of these

Ans: Option b. Is correct. Faraday demonstrated in the third experiment that relative motion is not required to induce a current in the primary coil. When an iron rod is inserted into the coils parallel to their axis, the deflection increases considerably.

5. When a magnet is brought close to a coil: 

(i) speedily 

(ii) slowly

 then induced e.m.f will be:

1. more in (i) case

2. less in (i) case

3. equal in both cases

4. depends on the radius of the ring

Ans: Option a. is correct. When a magnet is rapidly brought near a coil, the number of magnetic fields travelling through the coil changes more speedily, causing the coil to produce more emf.

When a magnet is slowly brought to a coil, the number of magnetic fields travelling through the coil varies slowly, causing the coil to induce less emf. 

6. The primary coil is attached to the galvanometer in Faraday and Henry's second experiment, while the secondary coil is connected to a battery. When the primary coil is rotated around its axis, then:

1. The current will induce in the primary coil

2. There will be no current generated in the primary coil 

3. The primary coil will create a momentary current.

4. Can't say.

Ans: Option b. Is correct. According to Faraday and Henry's second experiment, we can say that when a current-carrying coil is moved closer or away from another coil, an emf is induced in the coil.

• A current will get induced in the coil if the circuit in which the coil is connected is closed.

• To create a current in the coil, relative motion between the two coils is required.

• When the primary coil is rotated around its axis in the given situation, there will be no relative motion between the primary and secondary coils.

• There will be no current in the primary coil since there is no relative motion between the primary and secondary coils.

Fun Fact

Faraday has done some praiseworthy work in his years of discoveries. Along with his fellow scientist, Faraday derived words such as electrodes, anodes, and ions for his experiments and was considered futuristic names

Conclusion

This is all about the experiments conducted by Faraday and Henry with a simpler explanation. Focus on how they worked on such experiments and postulated the theories we study today. Study these experiments carefully and understand their outcomes.