Advertisements
Advertisements
प्रश्न
How is the working of an electric bell affected, if alternating current be used instead of direct current?
Advertisements
उत्तर
If an a.c. source is used in place of battery, the core of electromagnet will get magnetized, but the polarity at its ends will change. Since attraction of armature does not depend on the polarity of electromagnet, so the bell will still ring on pressing the switch.
संबंधित प्रश्न
The device used for producing electric current is called _________.
In which of the following case does the electromagnetic induction occur?
A loop of wire is held near a magnet.
Can a transformer work when it is connected to a D.C. source? Give a reason.
Fig. shows a simple form of an A.C. generator.
(a) Name the parts labeled A and B.
(b) What would be the effect of doubling the number of turns on the coil if the speed of rotation remains unchanged?
(c) Which of the output terminals is positive if the coil is rotating in the
direction shown in the diagram (anticlockwise)?
( d ) What is the position of the rotating coil when p.d. across its ends is zero? Explain why p.d. is zero when the coil is at this position .
(e) Sketch a graph showing how the p.d. across the ends of the rotating coil varies with time for an A.C. dynamo.
( f) On th e same sheet of paper and vertically below the first graph using the same time scale, sketch graphs to show the effect of
(i) Doubling the speed of rotation and at the same time keeping
the field and the number of turns constant,
(ii ) Doubling the number of turns on the coil and at the same time
doubling the speed of rotation of the coil, keeping th e speed
constant.
State the condition at which we say the two coils kept close to each other are perfectly coupled with each other.
What for an inductor is used? Give some examples.
Show that Lenz’s law is in accordance with the law of conservation of energy.
Obtain an expression for motional emf from Lorentz force.
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 ______.
For making a strong electromagnet the material of the core should be ______.
