Advertisements
Advertisements
प्रश्न
Consider the energy density in a solenoid at its centre and that near its ends. Which of the two is greater?
Advertisements
उत्तर
In a solenoid, energy is stored in the form of a magnetic field. If a constant current flows through the solenoid, the magnetic field inside is approximately uniform at the centre but decreases near the ends. The energy per unit volume (or energy density) in the magnetic field is given by `mu = B^2/(2mu_0)`.
Since B is stronger at the centre and weaker near the ends, the energy density is greater at the centre than near the ends.
APPEARS IN
संबंधित प्रश्न
The device used for producing electric current is called _________.
Name a common device that uses electromagnets.
State three ways in which the strength of an electromagnet can be increased.
Name two devices in which electromagnets are used and two devices where permanent magnets are used.
Describe different ways to induce current in a coil of wire.
Name and state the law which determines the direction of induced current.
or
State Fleming’s right-hand rule.
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.
The coil of a moving-coil galvanometer keeps on oscillating for a long time if it is deflected and released. If the ends of the coil are connected together, the oscillation stops at once. Explain.
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?
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.
Transformer______.
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.
State the purpose of soft iron core used in making an electromagnet.
What is an electromagnet? What do you know about the simplest form of an electromagnet?
Choose the correct option:
A conductor rod of length (l) is moving with velocity (v) in a direction normal to a uniform magnetic field (B). What will be the magnitude of induced emf produced between the ends of the moving conductor?
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 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 ______.
Induced current flows through a coil ______.
A coil of one turn is made of a wire of certain length and then from the same length, a coil of two turns is made. If the same current is passed in both the cases, then the ratio of the magnetic inductions at their centres will be:
Which of the following phenomena makes use of electromagnetic induction?
A conducting bar of length L is free to slide on two parallel conducting rails as shown in the figure
Two resistors R1 and R2 are connected across the ends of the rails. There is a uniform magnetic field `vec"B"` pointing into the page. An external agent pulls the bar to the left at a constant speed v. The correct statement about the directions of induced currents I1 and I2 flowing through R1 and R2 respectively is:
