Uses of Eddy Current

Q.

Ac and dc both can be measured by:

Q.

A moving coil galvanometer works on the principle that at equilibrium, the restoring torque and the torque experienced by the coil would be equal and based on that we calculate the deflection.But, at equilibrium shouldn't the angle be zer?

Q. How the net dipole moment of an atom for diamagnetic material is zero?

Q. What happens when a diamagnetic substance is placed in a varying magnetic field?

Q. What does q1 q2 >0 signify in electrostatics

Q.

Which of the following is not an application of eddy currents?

1. Induction furnace

2. Galvanometer damping

3. Speedometer of automobiles

4. X-ray crystallography

Q.

Define eddy current?

Q. Eddy currents are not used in

1. electromagnetic damping
2. speedometer of vehicles
3. induction furnace
4. diffraction of X-rays

Q. In which of the following devices, the eddy current effect is not used ?

1. Induction furnace
2. Magnetic breaking in train
3. Electromagnet
4. Electric heater

Q. Why moving coil galvanometer cannot measure alternating current.

Q.

The pointer of a dead-beat galvanometer gives a steady deflection because [MP PMT 1994]

1. Its frame is made of abonite

2. Its pointer is very light

3. Eddy currents are produced in the conducting frame over which the coil is wound

4. Its magnet is very strong

Q. Mention any two applications of eddy currents.

Q.

This section contains 1 Assertion-Reason type question, which has 4 choices (a), (b), (c) and (d) out of which ONLY ONE is correct.
इस खण्ड में 1 कथन-कारण प्रकार का प्रश्न है, जिसमें 4 विकल्प (a), (b), (c) तथा (d) दिये गये हैं, जिनमें से केवल एक सही है।

A : When a ferromagnetic material is inserted into the coil of a moving coil galvanometer, both the current and voltage sensitivity of the galvanometer decreases.
A : जब एक चल कुण्डली गैल्वेनोमीटर की कुण्डली के अन्दर एक लौह-चुम्बकीय पदार्थ को प्रवेशित किया जाता है, तब गैल्वेनोमीटर की धारा तथा वोल्टता सुग्राहिता दोनों घटती हैं।

R : Current sensitivity and voltage sensitivity are directly proportional to the magnetic induction in the coil.
R : धारा सुग्राहिता तथा वोल्टता सुग्राहिता दोनों, कुण्डली में चुम्बकीय प्रेरण के समानुपाती होती हैं।

1. Both (A) and (R) are true and (R) is the correct explanation of (A)
   
   (A) तथा (R) दोनों सही हैं तथा (R), (A) का सही स्पष्टीकरण है
2. Both (A) and (R) are true but (R) is not the correct explanation of (A)
   
   (A) तथा (R) दोनों सही हैं लेकिन (R), (A) का सही स्पष्टीकरण नहीं है
3. (A) is true but (R) is false
   
   (A) सही है लेकिन (R) गलत है
4. (A) is false but (R) is true
   
   (A) गलत है लेकिन (R) सही है

Q. Which of the following properties truly characterise ferromagnets ?

1. They are capable of being magnetised very strongly by a magnetic field
2. They retain a considerable amount of their magnetisation on removal of the applied field
3. They lose their ferromagnetism and become paramagnetic when the temperature is raised above a certain temperature.
4. The linear relation between magnetic field induction $\overrightarrow{B}$ and intensity of magnetisation $\overrightarrow{M}$ does not exist.
   

Q.

When Wheatstone bridge is in balance condition, the current through galvanometer will be

1. Zero

2. Depends upon the type of galvanometer.

3. Minimum

4. Maximum

Q. A magnetic needle kept in a non uniform magnetic field.it can experience a force or torque?

Q. If 2s-2p mixing is not oerative the which among the following is paramagnetic C2 Be2 B2 N2

Q. The working of magnetic braking of trains is based on

1. Steady current
2. Eddy current
3. Pulsating current
4. Alternating current

Q.

In the dead beat galvanometer, the coil is wound on a frame made of:

1. magnetic material

2. bad conductor

3. non magnetic material

4. good conductor

Q. In which of the following devices, the eddy current effect is not used ?

1. Induction furnace
2. Magnetic breaking in train
3. Electromagnet
4. Electric heater

Q. When a piece of iron is placed in a time varying magnetic field, it gets heated. Identify the possible reason of this heating.

1. Eddy current
2. Fleming's current
3. Faraday's current
4. None of the above

Q. A coil of insulating wire is connected to battery. If it is moved towards a galvanometer then its point gets deflected because

1. the number of turns in the galvanometer coil remains constant
2. induced current is produced in the coil
3. the coil behaves like a magnet
4. none of the above

Q. A moving coil galvanometer is based on the

1. heating effect of current
2. peltier effect of current
3. magnetic effect of current
4. chemical effect of current

Q. Describe the ways in which Eddy current are used to advantage.

Q. Which of the following is not an application of eddy currents.

1. Induction heater
2. Conductivity meters for non-magnetic metals
3. Skin effect
4. Coating Thickness Measurements

Q. A coil is suspended in a uniform magnetic field, with the plane of the coil parallel to the magnetic lines of force. When a current is passed through the coil it starts oscillating and it is very difficult to stop. But if an aluminium plate is placed near to the coil, it stops. This is due to :

1. induction of electrical charge on the plate
2. development of air current when the plate is placed
3. electromagnetic induction in the aluminium plate giving rise to electromagnetic damping
4. shielding of magnetic lines of force as aluminium is a paramagnetic material

Q. Two coils P and Q are lying parallels and very close to each other. Coil P is connected to an AC source whereas Q is connected to a sensitive galvanometer. On pressing key K

1. small variations are observed in the galvanometer for applied 50 Hz voltage
2. deflections in the galvanometer can be observed for applied voltage of 1 Hz to 2 Hz.
3. constant deflection will be observed in the galvanometer for 50 Hz supply voltage
4. no deflection in the galvanometer will be observed

Q. Use of eddy currents is done in the following except

1. Moving coil galvanometer
2. Electric brakes
3. Induction motor
4. Dynamo

Q. Assertion :The coil is bound over the metallic frame in moving coil galvanometer. Reason: The metallic frame help in making steady deflection without any oscillation.

1. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
2. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
3. Assertion is correct but Reason is incorrect
4. Both Assertion and Reason are incorrect

Q.

The pointer of a dead-beat galvanometer gives a steady deflection because [MP PMT 1994]

1. Eddy currents are produced in the conducting frame over which the coil is wound

2. Its magnet is very strong

3. Its pointer is very light

4. Its frame is made of abonite