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Induced electromotive force and current take place inside the magnetic field and the current is generated by changing the magnetic field. Faraday's law of electromagnetic Induction is associated with induced electromotive force and current. Induced electromagnetic force is a voltage that is created when magnetic flux is passed through a coil. An electrical effect is created on the opposite side of coil when a wave of current starts to flow in the wire.
Also read: Lenz’s law
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Key Terms: Force, Current, Faraday’s Law, Magnetic Field, Magnetic Flux, Electromotive Force, Induced Electromotive Force
Induced Electromotive Force
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Current can be induced in the coil by altering the magnetic field. Change in the magnetic field causes the current to flow. When magnetic flux changes while passing through a loop, an induced electromotive force is created. Induced electromotive force is used in transformers, galvanometers, and generators.
Induced Electromotive Force
Read More: Magnetic Field in A Solenoid
Electromotive Force
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When change in the magnetic field of an electrochemical cell produces electric potential, it is known as electromotive force or EMF. Electromotive force is work done on a unit electric charge because, in order to convert energy from one form to another, a battery or generator is used where one terminal is negatively charged whereas the other one is positively charged.
Electromotive force is used in electromagnetic flow meters.
Electromotive force is expressed as:
(ε) = v + lr
Where,
v = voltage
l = current
r = internal resistance
Electromotive Force
Also Read:
| Related Articles | ||
|---|---|---|
| Uses of Inductor | Transformers | Electromagnets |
| Electromagnetic Field | Motional emf | Experiment faraday henry |
Faraday’s Law
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Faraday’s law of electromagnetic induction consists of two laws. Induced electromotive force in a conductor is described in the first law and the second law deals with the amount of electromagnetic force produced in the conductor.
According to Faraday's first law of electromagnetic induction, an electromotive force is induced when a conductor is placed in a magnetic field that can be changed. Induced current is produced in a conductor if it is closed. Second Faraday's law of electromagnetic induction states that induced electromagnetic force in a coil is equivalent to the rate of change of flux.
ε = - N ΔΦΔt
Where, ε = induced voltage/ electromotive force
ΔΦ = change in the magnetic flux
Δt = change in time
N = number of loops
Faraday’s Law of Electromagnetic Induction Detailed Explanation
Faraday’s Laws of Electromagnetic Induction Video Explanation
Read More: Electromagnetism
Things to Remember
- The change in the flux of the conductor or coil induced electromotive force.
- Electromotive force is measured in volt.
- If electromotive force is obtained in a moving electric conductor, in the presence of a magnetic field, it is known as motional electromotive force.
- Emf can be induced either through change in magnetic flux in the circuit or through motion of conductor in the magnetic field.
- Concept of Lorentz force deals with the concept of induced electromotive force and current.
- Induced emf gives rise to a generation of potential difference in the coil because of change in magnetic flux.
- Induced emf is also known by the names of electromotive force induction, electromagnetic induction, and induced electromotive force.
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Previous Year Questions
- An electric buib rated 220 V, 100 W is connected in series with another bulb… [KEAM]
- A carbon resistor is marked with the ring coloured brown, black, green and gold….[KEAM]
- The effective resistance across the points A and I is...[KEAM]
- A metal conductor of length 1m rotates vertically about one...[KEAM]
- The north pole of a long horizontal bar magnet is being brought closer to a…
- what is the current flow through the resistor during the 0.4 s?
- Revolutions per minute in the earth's magnetic field (B=0.5 gauss), the emf induced in coil will be…
- Which of the following does not use the principle of electromagnetic induction?
- A uniform wire of resistance R and length L is cut into four equal parts…
- At room temperature, copper has free electron density of 8.4 times…
- Three resistances P, Q, R each of 2 Omega….
- A coil having 500 square loops of side 10 cm is placed….
- The north pole of a long horizontal bar magnet is being brought closer to….
- The current in a coil of L = 40 mH is to be… [VITEEE 2017]
- wo identical circular coils A and B are kept on a horizontal tube side by side without touching each other…. [KCET 2013]
- The magnetic flux through a circuit of resistance R changes by an amount….[NEET 2004]
- A conducting loop in the shape of a right angled isosceles triangle of height...[JEE Advance 2016]
- If a transformer of an audio amplifier has output impedance…..[JCECE]
- A wire loop is rotated in magnetic field. The frequency of change of direction of the induced e.m.f. is….[NEET 2013]
- An electron moves on a straight line path XY as shown. The abcd is a coil...[NEET 2015]
Sample Questions
Ques. What is the dimension of electromotive force? (2 Marks)
Ans. Dimension of electromotive force is M1L2T-3I-1. The ratio of work done on unit charge is known as EMF.
Emf = joules coulombs
Electromotive force is calculated in Volts.
Ques. How does the electromotive force affect the strings of an electric guitar? (2 Marks)
Ans. Electromotive force is created inside the coil when the strings of the electric guitar vibrate. The vibration of the guitar gives rise to the magnetization which is present in the string. The input of the guitar is connected to the two ends of the coil which are connected to the speaker.
Ques. What happens when a magnet is moved rapidly in a static coil? (2 Marks)
Ans. Because of the increase in the rate of change in the magnetic field, the induced electromotive force also increases. There is a change in the magnetic flux near the coil which depends on the rate of change in the magnetic field.
Ques. Differentiate between EMF and terminal voltage. (3 Marks)
Ans.
| Electromotive force | Terminal voltage |
|---|---|
| The maximum potential difference in the presence of a battery when there is no flow of current | The potential difference across the terminal keeping the circuit on. |
| It is measured by a potentiometer | It is measured by a voltmeter |
Ques. What are some of the common applications of Faraday’s law? (2 Marks)
Ans. Faraday’s law is applied in :
- Transformers
- Induction cooker follows principle of mutual induction
- Velocity of the fluid is recorded when an electromotive force is induced in an electromagnetic flowmeter
- Electric guitar and electric violin
Ques. What is magnetic flux? (2 Marks)
Ans. Number of magnetic field lines passing through a closed surface is known as magnetic flux. The area under consideration depends on the direction of the magnetic field. It is usually measured in flux meters and its SI unit is weber (wb). The formula is:
ΦB = B.A = BA cos θ
Where,
ΦB = magnetic flux
B= magnetic field
A = area
θ = the angle at which the field line passes
Ques. What are the factors on which the induced electromotive force depends? (2 Marks)
Ans. The factors on which the electromotive force depends are:
- Speed of the magnet moving into or out of the coil
- Cross-sectional area of the coil
- Magnetic strength
- Number of loops of wire
Ques. How to change the magnetic field intensity in a closed-loop? (2 Marks)
Ans. Intensity of magnetic field in a closed loop can be changed by:
- Rotation of the coil according to the magnet
- Movement of the coil in or out of the magnetic field
- Reducing or increasing the distance between the magnet and the coil
- Altering the area of the coil placed inside the magnetic field.
Ques. List some of the differences between potential difference and electromotive force. (3 Marks)
Ans.
| Potential difference | Electromotive difference |
|---|---|
| It is represented by V | It is represented by E |
| It changes over time | It remains unchanged |
| Defined as The energy which is lost as the unit charge pass through the component | Defined as work done on a unit charge |
| The resistance between the two points are taken into consideration | Exists without circuit resistance |
| The only electric field is induced | It gives rise to electrical, magnetic, and gravitation field |
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