Electromagnet

Q.

1.Material Suitable for making permanent magnet is:

a) Steel

b) Iron

c) copper

d) aluminium

Q. 45. A long solenoid is fabricated by closely winding a wire of radius 0.5 mm over a cylindrical non magnetic frame so that the successive turns nearly touch each other what would be the Magnetic field B at the centre of the solenoid if it carries a current of 5 ampere ??

Q.

Inside the magnet, the field lines move from the south pole to the north pole. Is this statement true?

1. True
2. False

Q. A cylindrical coil of current carrying wires resembling a spring is called a .

1. Solenoid
2. Loop
3. Motor
4. Generator

Q. 102.A solenoid wound over a rectangular frame. If all the linear dimensions of the frmae are increased by a factor of 3 and the number of turns per unit length remains the same, the self inductance increases by a factor of A 3 B 9 C 27 D 63

Q. Why a SOLENOID-: (a) is made up of long INSULATED wire
(b) made by winding wire over a NONCONDUCTING CYLINDRICAL TUBE

Q.

What is the difference between a bar magnet and U-shaped electromagnet.

Q.

(a) How does an electromagnet differ from a permanent magnet ?

(b) Name two devices in which electromagnets are used and two devices where permanent magnets are used.

Q. ntA short solenoid of length 4 cm, radius 2 cm and 100 turns is placed inside and on the axis of a long solenoid of length 80 cm and 1500 turns. A current of 3 A flows through the short solenoid. The mutual inductance of two solenoid isn

Q. What type of core should be put inside a current-carrying solenoid to make an electromagnet?

Q. What will happen if the copper wire used in the solenoid is not insulated?

Q.

What is the name given to a cylindrical coil whose diameter is less in comparison to its length?

1. Electromagnetic

2. Solenoid

3. Motor

4. Generator

Q. Which of the following material is used to prepare a core of an electromagnet?

1. Hard iron
2. Soft iron
3. Coloured iron
4. Rusted iron

Q.

Question 15
AB is a current carrying conductor in the plane of the paper as shown in Figure. What are the directions of magnetic fields produced by it at points P and Q? Given $r_1>r_2$, where will the strength of the magnetic field be larger?

Q. Question 14
Under what conditions permanent electromagnet is obtained if a current carrying solenoid is used? Support your answer with the help of a labelled circuit diagram.

Q. What is an insulated wire wound in the shape of a helix?

1. A toroid
2. A spring
3. A current generator
4. A solenoid

Q. A solenoid wound over a rectangular frame. If all the linear dimensions of the frame are increased by factor of 3 and number of turns per unit length remains the same , the self inductance increased by factor of- 1) 3 2) 9 3) 27 4) 63

Q.

An electromagnet retains the property of magnetism only until an ___________is passed through it.

Q.

Consider a circular loop of wire lying in the plane of the table. Let the current passing through the loop be clockwise. Apply the right hand rule to find out the direction of magnetic field inside and outside the loop? [2 MARKS]

Q.

In an electric fan electrical energy changes into mechanical energy.

1. True
2. False

Q.

A magnet which operates only when ________ flows through its insulated copper coil is called electromagnet.

Q. Why is a SOLENOID made by winding wire over a NONCONDUCTING cylindrical tube ?

Q. What is solenoid What factors affect the solenoid How to solenoid helps in flowing current

Q.

A crane uses a mysterious object ‘X’ to separate magnetic materials from junk. The object ‘X’ is most probably

1. Magnetic material

2. Permanent magnet

3. None of the above

4. Electromagnet

Q.

A current is flowing in a wire as shown. Choose the correct options regarding the magnetic field around the wire.

1. Directed into the screen at point S

2. Directed out of the screen at point Q

3. Doesn’t exist at axial points P and R

4. Doesn’t exist at outer points Q and S

Q. The needle of a magnetic compass does not deflect, when brought near a current carrying conductor.

1. True
2. False

Q.

A closely wounded cylindrical coil whose diameter is less in comparison to its length is named as:

1. Electro magnet

2. Helical magnet

3. Solenoid

4. none of these

Q. what are solenoids?

Q. a wire of fixed length is wound on a solenoid of length l and radius r . its self inductance is found to be L . now if same wire is wound on a solenoid of length l/2 and radius r/2 , then self inductance will be

Q. State the uses of electromagnets. [2 Marks]