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Experiments of Faraday and Henry were carried out in order to understand the phenomenon of Electromagnetic induction and its applications. Electromagnetic Induction is a phenomenon where an electric current is generated through a magnetic field. These experiments show how these experiments led to the development of generators and transformers that are used today. Faraday and Henry have conducted three experiments which we will go through in this article.
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Key Terms: Electromagnetic induction, magnetic field, generators, transformers, electric current, electricity, magnetic flux
NCERT Solutions of: Class 12 Physics Chapter 6 Electromagnetic Induction
What is Electromagnetic Induction?
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Electromagnetic Induction is the current induced by the magnetic field. It is a very cost-effective method and is related to magnets, induction, and electricity. Wireless charging that we see today is also possible due to electromagnetic induction.
Example- If you purchase something with a credit/debit card, the card is scanned or whipped through a machine. The magnetic chip presented on the card helps in the transaction. This is due to electromagnetic induction.
Electromagnetic Induction
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| Types of Generators and its Application | Magnetic Induction Formula | Induced electromotive force and current |
Electromagnetic Induction formula
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The formula for electromagnetic induction is presented as:
| e = N x dΦ/dt |
Here, e is the induced voltage
N is number of turns in the coil
Φ is the magnetic flux
T is time (in seconds)
Read also: Magnetic Induction Formula
Experiments of Faraday and Henry
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Experiment 1
- In this experiment, Faraday connected a coil with a galvanometer. A bar magnet is pushed towards the coil, in a way that the north pole is pointing toward the coil. As the bar magnet gets shifted, the pointer in the Galvanometer gets deflected which means that there is current present in the coil.
- It was seen that the bar magnet is stationary, the pointer shows no deflection and the motion lasts only till the magnet is in motion.
Experiments of Faraday and Henry
- The direction of deflection of the pointer depends upon the direction of motion of the bar magnet. Also, when a bar magnet is moved towards or away from the coil, deflections in the galvanometer are opposite as observed with the north pole for similar movements.
- The deflection of the pointer is larger or smaller depending upon the speed at which it is pulled towards or away from the coil. A similar effect is seen when instead of the bar magnet, the coil is moved and the magnet is held stationary. This shows that only the relative motion between the magnet and the coil is responsible for generating current in the coil.
Check Also: Faraday’s Law of Electromagnetic Induction and Its Application
Experiment 2
- Here, Faraday replaced the bar magnet with a second current-carry coil that is connected to the battery. The current in the coil due to the connected battery produced a steady magnetic field that made the system analogous to the previous one.
- As we move the coil toward the primary coil, the pointer in the galvanometer undergoes deflection, which shows the electric current is present in the first coil.
Experiments of Faraday and Henry
- As mentioned in the above case, here also the direction of the deflection of the pointer depends on the direction of movement of the secondary coil towards or away from the first.
- Also, the magnitude of deflection depends upon the speed in which the coil is moved. All these outcomes show that the system in the second case is analogous to the system in the first experiment.
Read Also: Electromagnetic Induction: Faraday’s Law of Induction
Experiment 3
- This experiment was conducted to prove that the relative motion between the coils was not really necessary for current in the primary coil to be generated.
- In this experiment, Faraday took two stationary coils and connected one of them to the galvanometer in the other coil showing a deflection, showing current is present in that.
- Also, the deflection in the pointer was not permanent and if pressed continuously, the pointer showed no deflection and when the key was released, the deflection occurred in the opposite direction.
Experiments of Faraday and Henry
Also Read: Electromagnetic Induction MCQ
Things to Remember
- Electromagnetic Induction is the current induced by the magnetic field.
- The formula for electromagnetic induction is presented as: e = N x dΦ/dt
- The magnetic field is the region around the moving magnetic charge within which the force of the magnet acts.
- The first experiment shows that there is relative motion between the coil and the magnetic field which induces a current.
- According to the second experiment, the degree to which deflection depends on the motion of the first coil to the second coil. Magnitude depends on the speed with which it moves.
- The third experiment shows that the relative motion is not necessary to produce current.
- It shows how these experiments led to the development of generators and transformers that are used today.
Also Read:
Sample Questions
Ques: What is Electromagnetic Induction? [2 Marks]
Ans: Electromagnetic Induction is the current induced by the magnetic field. Electromagnetic induction is a very cost-effective method. The word electromagnetic induction is related to magnets, induction and electricity.
Example- If you purchase something with a credit/debit card, the card is scanned or whipped through a machine. The magnetic chip presented on the card helps in the transaction. This is due to electromagnetic induction.
Ques: What are the applications of Electromagnetic Induction? [2 Marks]
Ans: The applications where electromagnetic induction is used are as follows-
- Some hard discs in computers work on the principle of electromagnetic induction.
- Graphic tablets or tablet computers where a special pen is used to draw digital images follow electromagnetic induction.
- Magnetic strip on credit/debit cards used for payments or ATM machines follows the principle of electromagnetic induction.
- AC generators work on the principle of electromagnetic induction.
- Electric transformers also use electromagnetic induction.
- The magnetic flow meter also follows the phenomenon of electromagnetic induction.
- The motors and machines that we use everyday work on the basis of electromagnetic induction.
Ques: Explain the Electromagnetic induction formula. [2 Marks]
Ans: The formula for electromagnetic induction is presented as
e = N x dΦ/dt
Here, e is the induced voltage
N is number of turns in the coil
Φ is the magnetic flux
T is time (in seconds)
Ques: What is the first experiment of Faraday and Henry? [2 Marks]
Ans: In this experiment, the coil is connected to a galvanometer. The bar magnet was pushed towards the coil, keeping the north pole pointing towards the coil. It was observed that the bar magnet shifted and the pointer in the galvanometer was deflected.
This shows that there is current present in the coil. The shift and deflection occurred when the magnet was in motion, not stationary. This shows that there is relative motion between the coil and the magnetic field that induces a current.
Ques: What is the second experiment of Faraday and Henry? [2 Marks]
Ans: In this experiment, the bar magnet of the circuit was replaced with another coil that generated current and connected with a battery. The coil connected to the battery produces a steady current. The second coil shows that the pointer in the galvanometer is deflected, indicating the presence of current in the coil.
The degree to which deflection depends on the motion of the first coil to the second coil. Magnitude depends on the speed it moves.
Ques: What is the third experiment of Faraday and Henry? [2 Marks]
Ans: The third experiment shows that the relative motion is not necessary to produce current. Both the coils are placed, one is connected to a battery and the other is connected to a galvanometer. But when pushed once, the pointer in the galvanometer is deflected.
Ques: What is a magnetic field? [1 Mark]
Ans: The magnetic field is the region around the moving magnetic charge within which the force of the magnet acts. Mathematically, the magnetic field is also described as a vector field. The density of magnetic field lines shows the strength of the magnetic field. The magnetic field also describes the magnetic force.
Previous Year Questions
- The direction of force acting on a current carrying conductor at right angles to a magnetic field is given by [KCET 1996]
- A wire in the form of a circular loop of one turn carrying a current produces a magnetic field B at the centre. If the same wire is looped into a coil of two turns and carries the same current, the new value of magnetic induction at the centre is...[KCET 2003]
- A motor….[KCET 1996]
- The primary winding of a transformer has 500 turns whereas its secondary has 5000 turns. The primary is connected to an A.C. supply 20 V, 50 Hz. The secondary will have an output of….[NEET 1997]
- A copper disc of radius 0.1m0.1m is rotated about its centre with 20rev/s20rev/s in a uniform magnetic field of 0.1T0.1T with its plane perpendicular to the field. The emf induced across the radius of the disc is:…...[KEAM 2006]
- A dynamo converts…..[UPSEE 2014]
- A magnetic field of 2×10−22×10−2T acts at right angles to a coil of area 100 cm2cm2, with 50 turns. The average e.m.f. induced in the coil is 0.1 V, when it is removed from the field in t sec. The value of t is….[NEET 1991]
- The current in a coil of L = 40 mH is to be increased uniformly from 1A to 11 A in 4 milli sec. The induced e.m.f. will be….[VITEEE 2017]
- A conducting circular loop is placed in a uniform magnetic field 0.04T0.04T with its plane perpendicular to the magnetic field. The radius of the loop starts shrinking at 2mm/s.2mm/s. The induced emf in the loop when the radius is 2cm2cm is…..[NEET 2009]
- A circular disc of radius 0.2 meter is placed in a uniform magnetic field of induction 1π(Wbm2)1π(Wbm2) in such a way that its axis makes an angle of 60∘∘ with →BB→ . The magnetic flux linked with the disc is…..[NEET 2008]
- In an ideal transformer, the voltage and the current in the primary are 200 V, 2A and that in the secondary are 2000 V, I A. The value of I is (A)….[KCET 1998]
- Direction of current induced in a wire moving in a magnetic field is found using…..[KCET 2012]
- Choke used to limit high frequency A.C. has…..[KCET 1998]
- An aluminium ring B faces an electromagnet A.The current I through A can be altered….[KCET 2001]
- An aircraft with a wingspan of 40m40m flies with a speed of 1080km/hr1080km/hr in the eastward direction at a constant altitude in the northern hemisphere, where the vertical component of the earth's magnetic field 1.75×10−51.75×10−5 TT. Then the emf developed between the tips of the wings is…….[KCET 2015]
- A 50HzAC current of peak value 2A flows through one of the pair of coils. If the mutual inductance between the pair of coils is 150mH, then the peak value of voltage induced in the second coil is….[KEAM]
- The eiectric field E, current density j and conductivity σσ of a conductor are related as…...[KEAM]
- The magnetic flux linked with a coil of NN turns of area of cross section AA held with its plane parallel to the field BB is….[KEAM]
- When 100 V d.c. is applied across a coil, a current of 1 A flows through it. When 100 V a.c. of 50 Hz is applied to the same coil only 0.5 A flows. The inductance of the coil is…..[KCET 2003]
- Near a circular loop of conducting wire as shown in the figure an electron moves along a straight line. The direction of the induced current if any in the loop is…..[KCET 2009]
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