An insulated copper wire wound on a cylindrical cardboard tube such that its length is greater than its diameter is called a solenoid. When an electric current is passed through the solenoid, it produces a magnetic field around it. The magnetic field produced by a current-carrying solenoid is similar to the magnetic field produced by a bar magnet. The field lines inside the solenoid are in the form of parallel straight lines. The strong magnetic field produced inside a current-carrying solenoid can be used to magnetise a piece of magnetic material like soft iron, when placed inside the solenoid. The strength of magnetic field produced by a current carrying solenoid is directly proportional to the number of turns and strength of current in the solenoid.
(i) The strength of magnetic field inside a long current -carrying straight solenoid is
(a) more at the ends than at the centre
(b) minimum in the middle
(c) same at all points
(d) found to increase from one end to the other.
(ii) The north-south polarities of an electromagnet can be found easily by using

(iii) For a current in a long straight solenoid N-and S-poles are created at the two ends.
Among the following statements, the incorrect statement is
(a) The field lines inside the solenoid are in the form of straight lines which indicates that the magnetic field is the same at all points inside the solenoid.
(b) The strong magnetic field produced inside the solenoid can be used to magnetise a piece of magnetic material like soft iron, when placed inside the coil.
(c) The pattern of the magnetic field associated with the solenoid is different from the pattern of the magnetic field around a bar magnet.
(d) The N- and S-poles exchange position when the direction of current through the solenoid is reversed.
(iv) A long solenoid carrying a current produces a magnetic field B along its axis. If the current is double and the number of turns per cm is halved, then new value of magnetic field is

(v) A soft iron bar is enclosed by a coil of insulated copper wire as shown in figure. When the plug of the key is closed, the face B of the iron bar marked as

A magnetic field is described by drawing the magnetic field lines. When a small north magnetic pole is placed in the magnetic field created by a magnet, it will experience a force. And if the north pole is free, it will move under the influence of magnetic field. The path traced by a north magnetic pole free to move under the influence of a magnetic field is called a magnetic field line. Since the direction of magnetic field line is the direction of force on a north pole, so the magnetic field lines always begin from the N-pole of a magnet and end on the S-pole of the magnet. Inside the magnet, however the direction of magnetic field lines is from the S-pole of the magnet to the N-pole of the magnet. Thus, the magnetic field lines are closed curves. When a small compass is moved along a magnetic field line, the compass needle always sets itself along the line tangential to it. So, a line drawn from the south pole of the compass needle to its north pole indicates the direction of the magnetic field at that point.

(i) The magnetic field lines
(a) intersect at right angle to one another
(b) intersect at an angle of 45° to each other
(c) do not cross one another
(d) cross at an angle of 60° to one another.
(ii) A strong bar magnet is placed vertically above a horizontal wooden board. The magnetic lines of force will be
(a) only in horizontal plane around the magnet
(b) only in vertical plane around the magnet
(c) in horizontal as well as in vertical planes around the magnet
(d) in all the planes around the magnet.
(iii) Magnetic field lines can be used to determine
(a) the shape of the magnetic field
(b) only the direction of the magnetic field
(c) only the relative strength of the magnetic field
(d) both the direction and the relative strength of the magnetic field.
(iv) The magnetic field lines due to a bar magnet are correctly shown in figure

(v) Which of the following is not true about magnetic field lines?
(a) Magnetic field lines are the closed and continuous curve.
(b) No two field lines can cross each other.
(c) Crowdness of field lines represents the strength of magnetic field.
(d) The direction of field lines is from the north pole to the south pole inside a bar magnet.

Andre Marie Ampere suggested that a magnet must exert an equal and opposite force on a current carrying conductor, which was experimentally found to be true. But we know that current is due to charges in motion. Thus, it is clear that a charge moving in a magnetic field experience a force, except when it is moving in a direction parallel to it. If the direction of motion is perpendicular to the direction of magnetic field, the magnitude of force experienced depends on the charge, velocity (v), strength of magnetic field (B), and sine of the angle between v and B. Direction of magnetic force is given by Fleming's left hand rule.

(i) If an electron is travelling horizontally towards east. A magnetic field in vertically downward direction exerts a force on the electron along

(ii) If a charged particle is moving along a magnetic field line. The magnetic force on the particle is

(iii) A magnetic field exerts no force on
(a) a stationary electric charge
(b) a magnet
(c) an electric charge moving perpendicular to its direction
(d) an unmagnetised iron bar
(iv) A uniform magnetic field exists in the plane of paper pointing from left to right as shown in figure. In the field an electron and a proton move as shown. The electron and the proton experience

(a) forces both pointing into the plane of paper
(b) forces both pointing out of the plane of paper
(c) forces pointing into the plane of paper and out of the plane of paper, respectively
(d) force pointing opposite and along the direction of the uniform magnetic field respectively
(v) An electron beam enters a magnetic field at right angles to it as shown in the figure. The direction of force acting on the electron beam will be

A current carrying wire produces magnetic field around it. The phenomena in which an electromotive force and current (if the conductor is in the form of a closed circuit) is induced by changing magnetic field (or by passing magnetic field lines) through it is called electromagnetic induction. The emf so developed is called induced emf and current made to flow is called induced current. The cause of induced emf carried out by Faraday and Henry. It can be concluded that the induced current flows in a conductor as long as the magnetic lines of force change within the conductor. In case of relative motion i.e., motion of coil w.r.t to magnet or vice versa, the direction of the current flowing in the conductor is determined by the direction of the relative motion of the conductor with respect to the magnetic field. The induced emf or current is directly proportional to the rate of change in magnetic field.

(i) A student connects a coil of wire with a sensitive galvanometer as shown in figure. He will observe the deflection in the galvanometer if bar magnet is

(a) placed near one of the faces of the coil and parallel to the axis of the coil
(b) placed near one of the faces of the coil and perpendicular to the axis of the coil
(c) placed inside the coil
(d) moved towards or away from the coil parallel to the axis of the coil.
(ii) A conducting rod AB moves across two magnets as shown in figure and the needle in the galvanometer deflects momentarily. What is the name of this physical phenomenon?

(iii) A bar magnet is pushed steadily into a long solenoid connected to a sensitive meter.

Which of the following would affect the magnitude of the deflection of the meter?
(a) How fast the magnet is pushed into the coil.
(b) The direction in which the coil is wound.
(c) The end of the solenoid the magnet enters.
(d) The pole of the magnet enters the coil first.
(iv) What is the condition of an electromagnetic induction?
(a) There must be a relative motion between galvanometer and coil of wire.
(b) There must be a relative motion between galvanometer and a magnet.
(c) There must be a relative motion between galvanometer and electric motor.
(d) There must be a relative motion between the coil of wire and a magnet.
(v) An induced emf is produced when a magnet is plunged into a coil. The magnitude of induced emf does not depend on

An electric motor is a rotating device that converts electrical energy into mechanical energy. Electric motor is used as an important component in electric fans, refrigerators, mixers, washing machines, computers, MP3 players, etc.

An electric motor consists of a rectangular coil ABCD of insulated copper wire. The coil is placed between the two poles of a magnetic field such that the arm AB and CD are perpendicular to the direction of the magnetic field. The ends of the coil are connected to the two halves P and Q of a split ring. The inner sides of these halves are insulated and attached to an axle. The external conducting edges of P and Q touch two conducting stationary brushes X and Y respectively, as shown in the figure. Commercial motors use an electromagnet in place of a permanent magnet, a large number of turns of conducting wire in the current carrying coil and a soft iron core on which the coil is wound.
(i) Choose incorrect statement from the following regarding split rings.
(a) Split rings are used to reverse the direction of current in coil.
(b) Split rings are also known as commutator.
(c) Split ring ii a discontinuous or a broken ring.
(d) Both (a) and (b)
(ii) Which of the following has no effect on the size of the turning effect on the coil of an electric motor?

(iii) When current is switched ON, an electric fan converts

(iv) In an electric motor, device that makes contact with the rotating rings and through them to supply current to coil is

(v) In an electric motor, the direction of current in the coil changes once in each

A solenoid is a long helical coil of wire through which a current is run in order to create a magnetic field. The magnetic field of the solenoid is the superposition of the fields due to the current through each coil. It is nearly uniform inside the solenoid and close to zero outside and is similar to the field of a bar magnet having a north pole at one end and a south pole at the other depending upon the direction of current flow. The magnetic field produced in the solenoid is dependent on a few factors such as, the current in the coil, number of turns per unit length etc.
The following graph is obtained by a researcher while doing an experiment to see the
variation of the magnetic field with respect to the current in the solenoid. The unit of magnetic field as given in the graph attached is in milli-Tesla (mT) and the current is given in Ampere.
(i) What type of energy conversion is observed in a linear solenoid?

(ii) What will happen if a soft iron bar is placed inside the solenoid?
(a) The bar will be electrocuted resulting in short-circuit.
(b) The bar will be magnetised as long as there is current in the circuit.
(c) The bar will be magnetised permanently.
(d) The bar will not be affected by any means.
(iii) The magnetic field lines produced inside the solenoid are similar to that of …
(a) a bar magnet
(b) a straight current carrying conductor
(c) a circular current carrying loop
(d) electromagnet of any shape
(iv) After analysing the graph a student writes the following statements.
    I. The magnetic field produced by the solenoid is inversely proportional to the current.
    II. The magnetic field produced by the solenoid is directly proportional to the current.
    III. The magnetic field produced by the solenoid is directly proportional to square of the current.
    IV. The magnetic field produced by the solenoid is independent of the current.
Choose from the following which of the following would be the correct statement(s).

(v) From the graph deduce which of the following statements is correct.

(a) For a current of 0.8A the magnetic field is 13 mT
(b) For larger currents, the magnetic field increases non-linearly.
(c) For a current of 0.8A the magnetic field is 1.3 mT
(d) There is not enough information to find the magnetic field corresponding to 0.8A current.

Ram is doing one experiment on Electromagnetic induction. He has a fixed coil of wire AB and he connected the two ends of the coil galvanometer. Now, he observe that when a bar magnet is held standstill inside the hollow coil of wire, then there is no deflection in the galvanometer pointer showing that no electric current is produced in the coil of wire when the magnet is held stationary in it. After that he moved bar magnet quickly into a fixed coil of wire AB. He observes that When a bar magnet is moved quickly into a fixed coil of wire AB, then a current is produced in the coil. This current causes a deflection in the galvanometer pointer [see Figure (a)]. Similarly, he observes that when the magnet is moved out quickly from inside the coil, even then a current is produced in the coil [see Figure (b)]. This current also causes a deflection in the galvanometer pointer but in the opposite direction (showing that when the direction of movement of magnet changes, then the direction of current produced in the coil also changes). So, he confirms that the current produced in this case is also alternating current or a.c.

(i) The phenomenon of electromagnetic induction is :
(a) the process of charging a body.
(b) the process of generating magnetic field due to a current passing through a coil.
(c) producing induced current in a coil due to relative motion between a magnet and the coil.
(d) the process of rotating a coil of an electric motor.
(ii) A soft iron bar is inserted inside a current-carrying solenoid. The magnetic field inside the solenoid :

(iii) The magnetic effect of current was discovered by :

(iv) The magnetic field inside a long straight solenoid carrying current :

(v) If the direction of electric current in a solenoid when viewed from a particular end is anticlockwise, then this end of solenoid will be :

The magnetic field pattern around a bar magnet is shown in adjoining Figure. This has been traced by using a plotting compass. The magnetic field lines leave the north pole of a magnet and enter its south pole. In other words, each magnetic field line is directed from the north pole of a magnet to its south pole. Each field line indicates, at every point on it, the direction of magnetic force that would act on a north pole if it were placed at that point. The strength of magnetic field is indicated by the degree of closeness of the field lines. Where the field lines are closest together, the magnetic field is the strongest.

(i) The magnetic field lines produced by a bar magnet :
(a) originate from the south pole and end at its north pole
(b) originate from the north pole and end at its east pole
(c) originate from the north pole and end at its south pole
(d) originate from the south pole and end at its west pole
(ii) The magnetic field lines :
(a) intersect at right angles to one another
(b) intersect at an angle of 45° to each other
(c) do not cross one another
(d) cross at an angle of 60° to one another
(iii) The north pole of earth’s magnet is in the :

(iv) A plotting compass is placed near the south pole of a bar magnet. The pointer of plotting compass will :
(a) point away from the south pole
(b) point parallel to the south pole
(c) point towards the south pole
(d) point at right angles to the south pole
(v) Which of the following statements is incorrect regarding magnetic field lines ?
(a) The direction of magnetic field at a point is taken to be the direction in which the north pole of a magnetic compass needle points.
(b) Magnetic field lines are closed curves
(c) If magnetic field lines are parallel and equidistant, they represent zero field strength
(d) Relative strength of magnetic field is shown by the degree of closeness of the field lines

When a current is passed through the circular loop of wire, a magnetic field lines near the coil are nearly circular and concentric. At the centre of the circular loop, the magnetic field lines are straight. The strength of the magnetic field produced by a current-carrying circular coil (or circular wire) depends on
(i) current flowing through the coil.
(ii) radius of the circular coil.
(iii) number of turns of wire in the circular coil. The direction of the field lines can be found by applying right-hand thumb rule.

(i) A long horizontal power line is carrying a current of 100 A in the east-west direction. What is the direction of magnetic field at a point 1.0 m below it?

(ii) State the pattern of magnetic field lines for current carrying circular conductor.
(a) Magnetic field lines will be concentric circles to any point of the circular loop
(b) At centre, the field lines appear straight
(c) Both of these
(d) None of these
(iii) If a current carrying straight conductor is placed in east-west direction, then find the direction of the force experienced by the conductor due to earth's magnetic field.

(iv) According to right-hand thumb rule direction of the curl of fingers of the right hand gives the

(v) In case of circular loop carrying current, the strength of magnetic field is
(a) constant everywhere
(b) stronger inside the loop than outside the loop
(c) weaker inside the loop than outside the loop
(d) none of these