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?
No deflection occurs when the conductor is placed in the plane of the paper itself since the magnetic field due to the conductor is also vertical. Maximum deflection occurs when the conductor is perpendicular to the plane of the paper and current in it is maximum.
Under what conditions is a permanent electromagnet obtained if a current-carrying solenoid is used? Support your answer.
The solenoid should be connected to a direct current source.
The rod inside the solenoid should be made of magnetic material such as steel.
AB is a current-carrying conductor in the plane of the paper. What are the directions of magnetic fields produced at points P and Q? Given \( r_1 > r_2 \), where will the magnetic field be stronger?
The magnetic field at P is into the plane of the paper and at Q is out of the plane of the paper. The strength is larger at Q because \( r_2 < r_1 \).
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? Give a reason.
The deflection increases because the magnetic field strength is directly proportional to the current in the conductor.
An electric current through a conductor produces a magnetic field around it. Is there a similar magnetic field around a thin beam of moving (i) alpha particles, (ii) neutrons? Justify your answer.
(i) Yes, alpha particles are positively charged and constitute a current when in motion.
(ii) Neutrons are electrically neutral; hence they produce no magnetic field.
What does the direction of thumb indicate in the right-hand thumb rule? How is this rule different from Fleming’s left-hand rule?
The thumb indicates the direction of current in the conductor. Fleming’s left-hand rule gives the direction of force on a current-carrying conductor in an external magnetic field.
Meena draws magnetic field lines of a current-carrying circular loop. As she moves away from the centre she observes that the lines keep on diverging. How will you explain her observation?
The magnetic field strength decreases with increasing distance from the loop, indicated by the decrease in closeness of field lines.
What does the divergence of magnetic field lines near the ends of a current-carrying straight solenoid indicate?
The divergence shows that the magnetic field strength decreases beyond the ends of the solenoid.
Name four appliances where an electric motor is used as an important component. In what respect are motors different from generators?
Electric fans, mixers, washing machines, and computer drives use electric motors.
Motors convert electrical energy into mechanical energy, whereas generators convert mechanical energy into electrical energy.
What is the role of the two conducting stationary brushes in a simple electric motor?
The brushes are connected to the battery and touch the outer sides of the split ring whose inner sides are insulated and attached to the axle.
What is the difference between a direct current and an alternating current? How many times does AC used in India change direction in one second?
DC flows in one direction only, while AC reverses direction periodically.
In India, AC frequency is 50 Hz, so it changes direction 100 times per second.
What is the role of a fuse used in series with any electrical appliance? Why should a fuse with a defined rating not be replaced by one with a larger rating?
A fuse protects appliances from short-circuiting or overloading by blowing off when excess current flows. A fuse with a larger rating would not blow in time and may damage appliances.