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
State three differences between direct current and alternating current.
Explain different ways to induce current in a coil.
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?
A conducting square loop of side l and resistance R moves in its plane with a uniform velocity v perpendicular to one of its sides. A uniform and constant magnetic field Bexists along the perpendicular to the plane of the loop as shown in figure. The current induced in the loop is _____________ .
A transformer has 400 turns in the primary winding and 10 turns in the secondary winding. The primary e.m.f. is 250 V and the primary current is 2.0 A. calculate:
(a) The secondary voltage,
(b) The secondary current, assuming 100% efficiency.
A thin semi-circular conducting ring (PQR) of radius r is falling with its plane vertical in a horizontal magnetic field B, as shown in the figure.
The potential difference developed across the ring when its speed v , is
State Lenz’s law.
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.
Name some equipment that uses electromagnetism for functioning.
