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प्रश्न
The device used for producing electric current is called _________.
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उत्तर
The device used for producing electric current is called a generator.
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संबंधित प्रश्न
Electric field intensity in free space at a distance ‘r’ outside the charged conducting sphere of radius ‘R’ in terms of surface charge density ‘ a ’ is............................
(a)`sigma / in_0[R/r]^2`
(b)`in_0/sigma[R/r]^2`
(c)`R/r[sigma/in_0]^2`
(d)`R/sigma[r/in_0]^2`
Two circular coils A and B are placed closed to each other. If the current in the coil A is changed, will some current be induced in the coil B? Give reason.
Name a common device that uses electromagnets.
State three ways in which the strength of an electromagnet can be increased.
State whether the following statement are true or false:
A motor works on the principle electric generator?
When current is 'switched on' and 'switched off' in a coil, a current is induced in another coil kept near it. What is this phenomenon known as?
An induced current is produced when a magnet is moved into a coil. The magnitude of induced current does not depend on:
(a) the speed with which the magnet is moved
(b) the number of turns of the coil
(c) the resistivity of the wire of the coil
(d) the strength of the magnet
Welders wear special glass goggles while working. Why? Explain.
Show diagrammatically how an alternating emf is generated by a loop of wire rotating in a magnetic field. Write the expression for the instantaneous value of the emf induced in the rotating loop.
A conducting rod is moved with a constant velocity v in a magnetic field. A potential difference appears across the two ends _____________ .
Calculate the dimensions of (a) \[\int \overrightarrow{E} . d \overrightarrow{l,}\] (b) vBl and (c) \[\frac{d \Phi_B}{dt}.\] The symbols have their usual meaning.
Figure shows a long U-shaped wire of width l placed in a perpendicular magnetic field B. A wire of length l is slid on the U-shaped wire with a constant velocity v towards right. The resistance of all the wires is r per unit length. At t = 0, the sliding wire is close to the left edge of the U-shaped wire. (a) Calculate the force needed to keep the sliding wire moving with a constant velocity v. (b) If the force needed just after t = 0 is F0, find the time at which the force needed will be F0/2.0
Can a transformer work when it is connected to a D.C. source? Give a reason.
The diagram 10 shows two coils X and Y. The coil X is connected to a battery S and a key K. The coil Y is connected to a galvanometer G.
When the key K is closed. State the polarity
(i)At the end of the coil X,
(ii)At the end C of the coil Y,
(iii)At the end C of the coil Y if the coil Y is (a) Moved towards the coil X, (b) Moved away from the coil X.
The following diagram shows a fixed coil of several turns connected to a center zero galvanometer G and a magnet NS which can move in the direction shown in the diagram.
- Describe the observation in the galvanometer if
- The magnet is moved rapidly,
- The magnet is kept still after it has moved into the coil
- The magnet is then rapidly pulled out the coil.
- How would the observation in (i) of part (a) change if a more powerful magnet is used?
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?
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.
What is an electromagnet? What do you know about the simplest form of an electromagnet?
Draw a labelled diagram to make an electromagnet from a soft iron bar. Mark the polarity at its ends in your diagram. What precaution would you observe while making it?
The diagram shows a rectangular coil ABCD, suspended freely between the concave pole pieces of a permanent horseshoe magnet, such that the plane of the coil is parallel to the magnetic field.
- State your observation when the current is switched on.
- Give an explanation for your observation in (i).
- State the rule, which will help you to find the motion of rotation of the coil.
- In which position will the coil ultimately come to rest?
- State four ways of increasing the magnitude of force acting on the coil.
The energy stored in a 50 mH inductor carrying a current of 4 A is ______
Fleming's left hand rule : electric current : : Fleming's right hand rule : _______
An electron moves on a straight-line path XY as shown in the figure. The coil abcd is adjacent to the path of the electron. What will be the direction of the current, if any, induced in the coil?
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.
A straight metal wire crosses a magnetic field of flux 4 mWb in a time 0.4 s. Find the magnitude of the emf induced in the wire.
A closely wound circular coil of radius 0.02 m is placed perpendicular to the magnetic field. When the magnetic field is changed from 8000 T to 2000 T in 6 s, an emf of 44 V is induced in it. Calculate the number of turns in the coil.
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.
Shown in the figure below is a metre bridge set up with null deflection in the galvanometer. The value of the unknown resistance R is ______
There is a uniform magnetic field directed perpendicular and into the plane of the paper. An irregular shaped conducting loop is slowly changing into a circular loop in the plane of the paper. Then ______.
A metal plate can be heated by ______.
If the sun radiates energy at the rate of 3.6 × 1033 ergs/sec the rate at which the sun is loosing mass is given by ______.
Sea turtles return to their birth beach many decades after they were born due to ______.
A rectangular, a square, a circular and an elliptical loop, all in the (x - y) plane, are moving out of a uniform magnetic field with a constant velocity `vecv = vhati`. The magnetic field is directed along the negative z-axis direction. The induced emf, during the passage of these loops, out of the field region, will not remain constant for ______.
An expression for oscillating electric field in a plane electromagnetic wave is given as Ez = 300 sin(5π × 103x - 3π × 1011t)Vm-1 Then, the value of magnetic field amplitude will be ______. (Given: speed of light in Vacuum c = 3 × 108 ms-1)
