Advertisements
Advertisements
प्रश्न
Answer the following:
State the principles of the electric motor and electric generator.
Advertisements
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.
APPEARS IN
संबंधित प्रश्न
When a bar magnet is pushed towards (or away) from the coil connected to a galvanometer, the pointer in the galvanometer deflects. Identify the phenomenon causing this deflection and write the factors on which the amount and direction of the deflection depends. State the laws describing this phenomenon.
A line charge λ per unit length is lodged uniformly onto the rim of a wheel of mass M and radius R. The wheel has light non-conducting spokes and is free to rotate without friction about its axis (Figure). A uniform magnetic field extends over a circular region within the rim. It is given by,
B = − B0 k (r ≤ a; a < R)
= 0 (otherwise)
What is the angular velocity of the wheel after the field is suddenly switched off?
If ‘R’ is the radius of dees and ‘B’ be the magnetic field of induction in which positive charges (q) of mass (m) escape from the cyclotron, then its maximum speed (vmax) is _______.
A) `(qR)/(Bm)`
B)`(qm)/(Br)`
C) `(qBR)/m`
D) `m/(qBR)`
What is an electromagnet? Describe the construction and working of an electromagnet with the help of a labelled diagram.
Write some of the important uses of electromagnets.
Name one device which works on the phenomenon of electromagnetic induction.
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.
Electromagnetic induction means ______.
Consider the energy density in a solenoid at its centre and that near its ends. Which of the two is greater?
Figure shows a long U-shaped wire of width l placed in a perpendicular magnetic field B. A wire of length l is slid on the U-shaped wire with a constant velocity v towards right. The resistance of all the wires is r per unit length. At t = 0, the sliding wire is close to the left edge of the U-shaped wire. (a) Calculate the force needed to keep the sliding wire moving with a constant velocity v. (b) If the force needed just after t = 0 is F0, find the time at which the force needed will be F0/2.0
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.
Complete the following diagram of a transformer and name the parts labeled A and B. Name the part you have drawn to complete the diagram . What is the material of this part? In this transformer a step-up or step-down? Why?
What is an electromagnet? List any two uses.
List two ways of increasing the strength of an electromagnet if the material of the electromagnet is fixed.
List some of the practical applications of an electromagnet.
Using Ampere's law, obtain an expression for the magnetic induction near a current-carrying straight infinitely long wire.
Which of the following scientist invented the rule of electromagnetic induction?
Write the two names in the following diagram.
Fleming’s right hand rule.
A square coil of side 30 cm with 500 turns is kept in a uniform magnetic field of 0.4 T. The plane of the coil is inclined at an angle of 30° to the field. Calculate the magnetic flux through the coil.
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.
An alternating emf of 0.2 V is applied across an L-C-R series circuit having R = 4Q, C = 80µF, and L = 200 mH. At resonance the voltage drop across the inductor is
Metal rings P and Q are lying in the same plane, where current I is increasing steadily. The induced current in metal rings is shown correctly in figure.
A cylindrical bar magnet is kept along the axis of a circular coil. If the magnet is rotated about its axis, then ____________.
A metal plate can be heated by ______.
The instrument that use to defect electric current in the circuit is known as ____________.
We can induce the current in a coil by ____________.
What should be the core of an electromagnet?
Ansari Sir was demonstrating an experiment in his class with the setup as shown in the figure below.
A magnet is attached to a spring. The magnet can go in and out of the stationary coil. He lifted the Magnet and released it to make it oscillate through the coil.
Based on your understanding of the phenomenon, answer the following question.
What is the principle which Ansari Sir is trying to demonstrate?
Ansari Sir was demonstrating an experiment in his class with the setup as shown in the figure below.
A magnet is attached to a spring. The magnet can go in and out of the stationary coil. He lifted the Magnet and released it to make it oscillate through the coil.
Based on your understanding of the phenomenon, answer the following question.
Consider the situation where the Magnet goes in and out of the coil. State two changes which could be made to increase the deflection in the galvanometer.
If the sun radiates energy at the rate of 3.6 × 1033 ergs/sec the rate at which the sun is loosing mass is given by ______.
Which of the following instruments works by electromagnetic induction?
Sea turtles return to their birth beach many decades after they were born due to ______.
AB is a coil of copper wire having a large number of turns. The ends of the coil are connected with a galvanometer as shown. When the north pole of a strong bar magnet is moved towards end B of the coil, a deflection is observed in the galvanometer.
- State the reason for using galvanometer in the activity and why does its needle deflects momentarily when magnet is moved towards the coil.
- What would be observed in the galvanometer in a situation when the coil and the bar magnet both move with the same speed in the same direction? Justify your answer.
- State the conclusion that can be drawn from this activity.
Will there be any change in the momentary deflection in the galvanometer if number of turns in the coil is increased and a more stronger magnet is moved towards the coil?
OR
What is electromagnetic induction? What is observed in the galvanometer when a strong bar magnet is held stationary near one end of a coil of large number of turns? Justify your answer.
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 ______.
One solenoid is centered inside another. The outer one has a length of 50.0 cm and contains 6750 coils, while the coaxial inner solenoid is 3.0 cm long and π cm2 in area and contains 150 coils. The current in the outer solenoid is changing at 3000 A/s. The emf induced in the inner solenoid is ______ V.
(Round off to two decimal places.)
