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प्रश्न
State Fleming’s right-hand rule.
What is right hand rule?
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उत्तर
- The Thumb, index finger, and middle finger of the right hand are stretched perpendicular to each other.
- The index finger indicates the direction of the magnetic field.
- Thumb indicates the direction of motion of the conductor.
- The middle finger indicates the direction of induced current.
संबंधित प्रश्न
The magnetic flux through a loop varies according to the relation Φ = 8t2 + 6t + C, where ‘C’ is constant, 'Φ' is in milliweber and 't' is in second. What is the magnitude of induced e.m.f. in the loop at t = 2 seconds.
A solenoid of length 1.5 m and 4 cm in diameter possesses 10 turns per metre. A current of 5 A is flowing through it. The magnetic induction at a point inside the solenoid along the axis is ............................. .
(μ0 = 4π × 10-7 Wb/Am)
- π × 10-5 T
- 2π × 10-5 T
- 3π × 10-5 T
- 4π × 10-5 T
State three differences between direct current and alternating current.
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 rectangular wire loop of sides 8 cm and 2 cm with a small cut is moving out of a region of uniform magnetic field of magnitude 0.3 T directed normal to the loop. What is the emf developed across the cut if the velocity of the loop is 1 cm s−1 in a direction normal to the
- longer side,
- shorter side of the loop?
For how long does the induced voltage last in each case?
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?
The magnetic flux through a loop is varying according to a relation `phi = 6t^2 + 7t + 1` where `phi` is in milliweber and t is in second. What is the e.m.f. induced in the loop at t = 2 second?
What is electromagnetic induction?
Prove theoretically (electromagnetic induction) `e = (dphi)/(dt)`
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)`
A circular coil of cross-sectional area 200 cm2 and 20 turns is rotated about the vertical diameter with angular speed of 50 rad s−1 in a uniform magnetic field of magnitude 3.0 × 10−2T. Calculate the maximum value of the current in the coil.
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.
State whether the following statement are true or false:
A motor works on the principle electric generator?
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?
Name one device which works on the phenomenon of electromagnetic induction.
Describe different ways to induce current in a coil of wire.
An induced current is produced when a magnet is moved into a coil. The magnitude of induced current does not depend on:
(a) the speed with which the magnet is moved
(b) the number of turns of the coil
(c) the resistivity of the wire of the coil
(d) the strength of the magnet
- What kind of energy change takes place when a magnet is moved towards a coil having a galvanometer at its ends?
- Name the phenomenon.
In which of the following case does the electromagnetic induction occur?
A loop of wire is held near a magnet.
A light metal disc on the top of an electromagnet is thrown up as the current is switched on. Why? Give reason.
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.
Consider the energy density in a solenoid at its centre and that near its ends. Which of the two is greater?
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 conducting rod is moved with a constant velocity v in a magnetic field. A potential difference appears across the two ends _____________ .
Can a transformer work when it is connected to a D.C. source? Give a reason.
Draw a simple labeled diagram of a step-down transformer.
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.
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.
A. C. generator______.
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?
Name the following diagram and explain the concept behind it.
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 Fleming’s Right Hand Rule.
List two ways of increasing the strength of an electromagnet if the material of the electromagnet is fixed.
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?
The energy stored in a 50 mH inductor carrying a current of 4 A is ______
State the condition at which we say the two coils kept close to each other are perfectly coupled with each other.
Observe the given figure of Fleming’s Right Hand Rule and write the labels of A and B correctly.
Find the odd one out and give its explanation.
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 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.
A coil of 200 turns carries a current of 4 A. If the magnetic flux through the coil is 6 x 10-5 Wb, find the magnetic energy stored in the medium surrounding the coil.
A 50 cm long solenoid has 400 turns per cm. The diameter of the solenoid is 0.04 m. Find the magnetic flux linked with each turn when it carries a current of 1 A.
A cylindrical bar magnet is kept along the axis of a circular coil. If the magnet is rotated about its axis, then ____________.
A cylindrical bar magnet (A) and similar unmagnetized cylindrical iron bar (B) are dropped through metallic pipe. The time taken to come down by ____________.
A metal plate can be heated by ______.
The instrument that use to defect electric current in the circuit is known as ____________.
What should be the core of an electromagnet?
Induced current flows through a coil ______.
For making a strong electromagnet the material of the core should be ______.
Sea turtles return to their birth beach many decades after they were born due to ______.
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:
A rectangular, a square, a circular and an elliptical loop, all in the (x - y) plane, are moving out of a uniform magnetic field with a constant velocity `vecv = vhati`. The magnetic field is directed along the negative z-axis direction. The induced emf, during the passage of these loops, out of the field region, will not remain constant for ______.
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:
Which scientists established in the early nineteenth century that electricity and magnetism are related?
What can produce a current in a coil even when the coil does not move?
Which movement of a coil can produce a current?
What change can produce a current in a stationary conductor?
Which change in the current of a nearby solenoid coil can produce an induced current?
