Advertisements
Advertisements
प्रश्न
A light metal disc on the top of an electromagnet is thrown up as the current is switched on. Why? Give reason.
Advertisements
उत्तर
When the current begins to grow through the electromagnet, the magnetic flux through the disc begins to increase. This sets up eddy current in the disc in the same direction as that of the electromagnetic current. Thus, if the upper surface of electromagnet acquires N-polarity, the lower surface of the disc also acquires N-polarity. As same magnetic poles repel each other, the light metallic disc is thrown up.
APPEARS IN
संबंधित प्रश्न
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.
A horizontal straight wire 10 m long extending from east to west is falling with a speed of 5.0 m s−1, at right angles to the horizontal component of the earth’s magnetic field, 0.30 × 10−4 Wb m−2.
- What is the instantaneous value of the emf induced in the wire?
- What is the direction of the emf?
- Which end of the wire is at the higher electrical potential?
In which of the following case does the electromagnetic induction occur?
A magnet is moved through a loop of wire .
The switches in figure (a) and (b) are closed at t = 0 and reopened after a long time at t = t0.
(a) The charge on C just after t = 0 is εC.
(b) The charge on C long after t = 0 is εC.
(c) The current in L just before t = t0 is ε/R.
(d) The current in L long after t = t0 is ε/R.
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.
Using Ampere's law, obtain an expression for the magnetic induction near a current-carrying straight infinitely long wire.
Fleming's left hand rule : electric current : : Fleming's right hand rule : _______
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 ______
Which of the following instruments works by electromagnetic induction?
A galvanometer is an instrument that can detect the presence of a current in a circuit.
