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प्रश्न
What is electromagnetic induction?
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उत्तर
The phenomenon of producing an induced e.m.f in a conductor or conducting coil due to changing magnetic flux is called electromagnetic induction.
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संबंधित प्रश्न
A solenoid of length 1.5 m and 4 cm in diameter possesses 10 turns per metre. A current of 5 A is flowing through it. The magnetic induction at a point inside the solenoid along the axis is ............................. .
(μ0 = 4π × 10-7 Wb/Am)
- π × 10-5 T
- 2π × 10-5 T
- 3π × 10-5 T
- 4π × 10-5 T
The device used for producing electric current is called _________.
State three differences between direct current and alternating current.
A metal rod `1/sqrtpi `m long rotates about one of its ends perpendicular to a plane whose magnetic induction is 4 x 10-3 T. Calculate the number of revolutions made by the rod per second if the e.m.f. induced between the ends of the rod is 16 mV.
When a bar magnet is pushed towards (or away) from the coil connected to a galvanometer, the pointer in the galvanometer deflects. Identify the phenomenon causing this deflection and write the factors on which the amount and direction of the deflection depends. State the laws describing this phenomenon.
A rectangular wire loop of sides 8 cm and 2 cm with a small cut is moving out of a region of uniform magnetic field of magnitude 0.3 T directed normal to the loop. What is the emf developed across the cut if the velocity of the loop is 1 cm s−1 in a direction normal to the
- longer side,
- shorter side of the loop?
For how long does the induced voltage last in each case?
The magnetic flux through a loop is varying according to a relation `phi = 6t^2 + 7t + 1` where `phi` is in milliweber and t is in second. What is the e.m.f. induced in the loop at t = 2 second?
A circular coil of cross-sectional area 200 cm2 and 20 turns is rotated about the vertical diameter with angular speed of 50 rad s−1 in a uniform magnetic field of magnitude 3.0 × 10−2T. Calculate the maximum value of the current in the coil.
Name a common device that uses electromagnets.
An emf of 2V is induced in a coil when the current in it is changed from 0A to 10A in 0·40 sec. Find the coefficient of self-inductance of the coil.
Explain why, an electromagnet is called a temporary magnet.
State the factors on which the strength of an electromagnet depends. How does it depend on these factors?
The direction of current in the coil at one end of an electromagnet is clockwise. This end of the electromagnet will be:
(a) north pole
(b) east pole
(c) south pole
(d) west pole
The most suitable material for making the core of an electromagnet is:
(a) soft iron
(b) brass
(c) aluminium
(d) steel
State whether the following statement are true or false:
A generator works on the principle of electromagnetic induction.
State whether the following statement are true or false:
A motor works on the principle electric generator?
Describe one experiment to demonstrate the phenomenon of electromagnetic induction.
In which of the following case does the electromagnetic induction occur?
The current is stopped in a wire held near a loop of wire .
In which of the following case does the electromagnetic induction occur?
A magnet is moved through a loop of wire .
In which of the following case does the electromagnetic induction occur?
A loop of wire is held near a magnet.
Consider the energy density in a solenoid at its centre and that near its ends. Which of the two is greater?
A conducting rod is moved with a constant velocity v in a magnetic field. A potential difference appears across the two ends _____________ .
L, C and R represent the physical quantities inductance, capacitance and resistance respectively. Which of the following combinations have dimensions of frequency?
(a) `1/(RC)`
(b) `R/L`
(c) `1/sqrt(LC)`
(d) C/L
Draw and label the diagram of a simple D.C. motor.
(a) Explain the rotation of the coil, giving a reason for your answer.
(b) How can you reverse the direction of rotation of the armature?
(c) How can you increase the speed of rotation of the motor?
Fill in the blanks by writing (i) Only soft iron, (ii) Only steel, (iii) Both soft-iron and steel for the material of core and/or magnet.
D.C. motor ______.
Fill in the blanks by writing (i) Only soft iron, (ii) Only steel, (iii) Both soft-iron and steel for the material of core and/or magnet.
A. C. generator______.
A coil has a self-inductance of 0·05 Henry. Find the magnitude of the emf induced in it when the current flowing through it is changing at the rate of 100 As-1.
State Fleming’s Right Hand Rule.
Draw a labelled diagram to show how an electromagnet is made.
List two ways of increasing the strength of an electromagnet if the material of the electromagnet is fixed.
What is an electromagnet? What do you know about the simplest form of an electromagnet?
Choose the correct option:
A conductor rod of length (l) is moving with velocity (v) in a direction normal to a uniform magnetic field (B). What will be the magnitude of induced emf produced between the ends of the moving conductor?
Observe the given figure of Fleming’s Right Hand Rule and write the labels of A and B correctly.
The right-hand thumb rule is also called _______ rule.
Which of the following scientist invented the rule of electromagnetic induction?
State Fleming’s right-hand rule.
What for an inductor is used? Give some examples.
Give an illustration of determining direction of induced current by using Lenz’s law.
Show that Lenz’s law is in accordance with the law of conservation of energy.
A square coil of side 30 cm with 500 turns is kept in a uniform magnetic field of 0.4 T. The plane of the coil is inclined at an angle of 30° to the field. Calculate the magnetic flux through the coil.
An induced current of 2.5 mA flows through a single conductor of resistance 100 Ω. Find out the rate at which the magnetic flux is cut by the conductor.
A coil of 200 turns carries a current of 4 A. If the magnetic flux through the coil is 6 x 10-5 Wb, find the magnetic energy stored in the medium surrounding the coil.
A 50 cm long solenoid has 400 turns per cm. The diameter of the solenoid is 0.04 m. Find the magnetic flux linked with each turn when it carries a current of 1 A.
A coil of 200 turns carries a current of 0.4 A. If the magnetic flux of 4 mWb is linked with each turn of the coil, find the inductance of the coil.
Using Lenz’s law, predict the direction of induced current in conducting rings 1 and 2 when the current in the wire is steadily decreasing.
An alternating emf of 0.2 V is applied across an L-C-R series circuit having R = 4Q, C = 80µF, and L = 200 mH. At resonance the voltage drop across the inductor is
A cylindrical bar magnet (A) and similar unmagnetized cylindrical iron bar (B) are dropped through metallic pipe. The time taken to come down by ____________.
A generator has an e.m.f. of 440 Volt and internal resistance of 4000 hm. Its terminals are connected to a load of 4000 ohm. The voltage across the load is ______.
The condition for the praenomen of electromagnetic induction is that there must be a relative motion between ____________.
The instrument that use to defect electric current in the circuit is known as ____________.
We can induce the current in a coil by ____________.
What should be the core of an electromagnet?
Ansari Sir was demonstrating an experiment in his class with the setup as shown in the figure below.
A magnet is attached to a spring. The magnet can go in and out of the stationary coil. He lifted the Magnet and released it to make it oscillate through the coil.
Based on your understanding of the phenomenon, answer the following question.
Consider the situation where the Magnet goes in and out of the coil. State two changes which could be made to increase the deflection in the galvanometer.
Induced current flows through a coil ______.
Which of the following instruments works by electromagnetic induction?
For making a strong electromagnet the material of the core should be ______.
A coil of one turn is made of a wire of certain length and then from the same length, a coil of two turns is made. If the same current is passed in both the cases, then the ratio of the magnetic inductions at their centres will be:
The working of a dynamo is based on the principle of
AB is a coil of copper wire having a large number of turns. The ends of the coil are connected with a galvanometer as shown. When the north pole of a strong bar magnet is moved towards end B of the coil, a deflection is observed in the galvanometer.
- State the reason for using galvanometer in the activity and why does its needle deflects momentarily when magnet is moved towards the coil.
- What would be observed in the galvanometer in a situation when the coil and the bar magnet both move with the same speed in the same direction? Justify your answer.
- State the conclusion that can be drawn from this activity.
Will there be any change in the momentary deflection in the galvanometer if number of turns in the coil is increased and a more stronger magnet is moved towards the coil?
OR
What is electromagnetic induction? What is observed in the galvanometer when a strong bar magnet is held stationary near one end of a coil of large number of turns? Justify your answer.
In the given circuit, initially switch S1 is closed and S2 and S3 are open. After charging of capacitor, at t = 0, S1 is open and S2 and S3 are closed. If the relation between inductance capacitance and resistance is L = 4CR2 then the time (in sec) after which current passing through capacitor and inductor will be same is ______ × 10-4 N. (Given R = ℓn(2)mΩ, L = 2mH)
A current I = 10 sin(100π t) A is passed in first coil, which induces a maximum e.m.f of 5π volt in second coil. The mutual inductance between the coils is ______.
The primary of a transformer has 400 turns while the secondary has 2000 turns. If the power output from the secondary at 1000 Vis 12 kW, what is the primary voltage?
A sheet is placed on horizontal surface in front of a strong magnetic pole. A force is needed to:
- hold the sheet there if it is magnetic.
- hold the sheet there if it is non-magnetic.
- move the sheet away from the pole with uniform velocity if it is conducting.
- move the sheet away from the pole with uniform velocity if it is both, non-conducting and nonpolar.
Choose the correct statement(s) from the options given below:
