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What is the role of the two conducting stationary brushes in a simple electric motor?

c) Both The two conducting stationary brushes draw current from the battery and supply it to the armature of the motor as they touch the outer... View Article

Name four appliances wherein an electric motor, a rotating device that converts electrical energy to mechanical energy, is used as an important component. In what respect motors are different from generators?

Vacuum cleaners,Washing Machines, Air conditioners, Grinders and mixers are a few home appliances that use electric motors. The difference... View Article

What does the divergence of magnetic field lines near the ends of a current-carrying straight solenoid indicate?

When a current passes through it, it creates a nearly uniform magnetic field inside or along the axis of the solenoid. Outside the coil or... View Article

Meena draws magnetic field lines of the field close to the axis of a current-carrying circular loop. As she moves away from the centre of the circular loop she observes that the lines keep on diverging. How will you explain her observation?

With a decrease in the distance strength of the magnetic field decreases. The decrease in degree of closeness of the lines of field indicates it.... View Article

What does the direction of thumb indicate in the right-hand thumb rule? In what way this rule is different from Fleming’s left-hand rule?

Thumb held by curled fingers indicates the direction of current in right hand rule whereas in fleming’s left hand rule force experienced by... View Article

It is established that an electric current through a metallic conductor produces a magnetic field around it. Is there a similar magnetic field produced around a thin beam of moving (i) alpha particles, (ii) neutrons? Justify your answer.

(i) Yes (ii) No. Alpha particles are positively charged particles and therefore a thin beam of moving alpha particles constitutes a current in... View Article

A magnetic compass shows a deflection when placed near a current-carrying wire. How will the deflection of the compass get affected if the current in the wire is increased? Support your answer with a reason.

It the current is increased in the conductor the deflection of the compass needle increases. This is because the strength of magnetic field... View Article

AB is a current-carrying conductor in the plane of the paper as shown in the figure. What are the directions of magnetic fields produced by it at points P and Q? Given r1 > r2, where will the strength of the magnetic field be larger?

By applying the right-hand thumb rule, the direction of magnetic field would be anti-clockwise as shown in diagram around the direction of... View Article

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.

Closed-circuit Core of soft iron When a ferromagnetic material rod is permanently placed inside the solenoid, the metal greatly increases the... View Article

A magnetic compass needle is placed in the plane of paper near point A. In which plane should a straight current-carrying conductor be placed so that it passes through A and there is no change in the deflection of the compass? Under what condition is the deflection maximum and why?

In the plane of the paper itself. The axis of the compass is vertical and the field due to the conductor is also vertical. It could result in a... View Article

The most important safety method used for protecting home appliances from short-circuiting or overloading is (a) earthing (b) use of fuse (c) use of stabilizers (d) use of electric meter

b) use of fuse The primary use of an electric fuse is to protect electrical equipment from excessive current and to prevent short circuits or... View Article

To convert an AC generator into DC generator (a) split-ring type commutator must be used (b) slip rings and brushes must be used (c) a stronger magnetic field has to be used (d) a rectangular wire loop has to be used

a) split-ring type commutator must be used A split-ring commutator makes the current change direction every alternate half-rotation, whereas a... View Article

The strength of the 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

(c) same at all points Inside the solenoid magnetic field lines are straight. This indicates strong magnetic field. Hence, magnetic field is... View Article

A constant current flows in a horizontal wire in the plane of the paper from east to west as shown in Figure. The direction of the magnetic field at a point will be North to South (a) directly above the wire (b) directly below the wire (c) at a point located in the plane of the paper, on the north side of the wire (d) at a point located in the plane of the paper, on the south side of the wire

b) directly below the wire The Fleming's right-hand rule shows the direction of induced current when a conductor moves in a magnetic field. The... View Article

Choose the incorrect statement (a) Fleming’s right-hand rule is a simple rule to know the direction of induced current (b) The right-hand thumb rule is used to find the direction of magnetic fields due to current-carrying conductors (c) The difference between the direct and alternating currents is that the direct current always flows in one direction, whereas the alternating current reverses its direction periodically (d) In India, the AC changes direction after every 1/50 second

d) In India the AC changes direction after every 1/50 second Fleming's right-hand rule shows the direction of induced current when a conductor... View Article

In the arrangement shown in the figure there are two coils wound on a non-conducting cylindrical rod. Initially, the key is not inserted. Then the key is inserted and later removed. Then (a) the deflection in the galvanometer remains zero throughout (b) there is a momentary deflection in the galvanometer but it dies out shortly and there is no effect when the key is removed (c) there are momentary galvanometer deflections that die out shortly; the deflections are in the same direction (d) there are momentary galvanometer deflections that die out shortly; the deflections are in opposite directions

d) there are momentary galvanometer deflections that die out shortly, the deflections are in opposite directions In the figure, two coils... View Article

Commercial electric motors do not use (a) an electromagnet to rotate the armature (b) effectively large number of turns of conducting wire in the current-carrying coil (c) a permanent magnet to rotate the armature (d) a soft iron core on which the coil is wound

c) a permanent magnet to rotate the armature In an electric motor, a rectangular coil is placed in between the magnetic field and when current... View Article

A uniform magnetic field exists in the plane of paper pointing from left to right as shown in the 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

(a) forces both pointing into the plane of the paper For the given figure, the proton and electron are moving in opposite directions to each... View Article

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

(c) The pattern of the magnetic field associated with the solenoid is different from the pattern of the magnetic field around a bar magnet. The... View Article

A circular loop placed in a plane perpendicular to the plane of paper carries a current when the key is ON. The current as seen from points A and B (in the plane of the paper and on the axis of the coil) is anti-clockwise and clockwise respectively. The magnetic field lines point from B to A. The N-pole of the resultant magnet is on the face close to (a) A (b) B (c) A if the current is small, and B if the current is large (d) B if the current is small and A if the current is large

(a) A The direction of the magnetic field will be from south to north pole. Point A is showing North Pole because field lines are pointing... View Article

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