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प्रश्न
Answer the following:
State the principles of the electric motor and electric generator.
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उत्तर
- Principle of electric motor:
Electric motor works on the principle that a current carrying conductor placed in a magnetic field experiences a force. - Principle of electric generator:
Electric generator works on the principle of electromagnetic induction. When the coil of electric generator rotates in a magnetic field. The magnetic field induces a current in this coil. This induced current then flows into circuit connected to the coil.
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संबंधित प्रश्न
State three differences between direct current and alternating current.
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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?
Prove theoretically (electromagnetic induction) `e = (dphi)/(dt)`
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.
How does an electromagnet differ forma permanent magnet?
Name two devices in which electromagnets are used and two devices where permanent magnets are used.
Explain why, an electromagnet is called a temporary magnet.
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
Describe different ways to induce current in a coil of wire.
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 .
Welders wear special goggles or face masks with glass windows to protect their eyes from electromagnetic radiations. Name the radiations and write the range of their frequency.
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(a) `1/(RC)`
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(c) `1/sqrt(LC)`
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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.
Draw and label the diagram of a simple D.C. motor.
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(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.
A. C. generator______.
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State the condition at which we say the two coils kept close to each other are perfectly coupled with each other.
Fleming's left hand rule : electric current : : Fleming's right hand rule : _______
Write the two names in the following diagram.
Right hand thumb rule.
State Fleming’s right-hand rule.
Give an illustration of determining direction of induced current by using Lenz’s law.
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.
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 ______
A metal plate can be heated by ______.
Name some equipment that uses electromagnetism for functioning.
A 0.4 m wire, stretched horizontally, carries an electric current of 15 A, in a magnetic field whose magnetic field intensity is 0.1 N/Am. What is the magnitude of the wire?
The working of a dynamo is based on the principle of
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 charge will flow through a galvanometer of resistance 200Ω connected to a 400Ω circular coil of 1000 turns wound on a wooden stick 20 mm in diameter, if a magnetic field B = 0.012 T parallel to the axis of the stick decreased suddenly to zero, is near ______.
