Ans. The cold resistance of the coil of the iron is much smaller than when it is hot . So when the iron is switched on , there is a large drop of voltage and consequently the bulb do not receive the proper voltage . As the coil gets heated , its resistance increases and so the voltage drop is made up when it is fully heated . This is why after some time the bulbs regain their brilliance .
Ans. No , the amount of positive and negative charge in any elementary volume remains the same though the electrons are in motion . So a current carrying conductor is electrically neutral .
Ans : When the plastic parts is removed , the capacitance of the metal dies decreases but the charge (developed by friction ) remains unchanged and so the voltage increases in compliance with the formula Q = CV
Ans : The field inside is zero (there is electrostatic screening )
Q . An electron moves along a metal tube with variable cross – section . How will its velocity change when it approaches the neck of the of the tube ?
Ans : Positive induced charges will appear on the neck of the tube and accelerate the electron
Ans : It will stick readily to the conducting wall because the same amount of charge is induced on the wall . But on the insulating wall , less amount of charge is induced . Due to greater force of attraction , it will stick more readily to the conducting wall.