Physics
Which of the following statements are correct ?
(i) An electromagnet produces a permanent magnetic field.
(ii) An electromagnet can produce a strong magnetic field.
(iii) The polarity of electromagnet can be reversed by reversing the direction of current in the solenoid.
- all of the above
- (i) and (ii)
- (ii) and (iii)
- (i) and (iii)
Related Questions
Look at the figure and answer the following questions:
(i) The end P becomes:
- south pole
- north pole
- cannot say
- none of the above
(ii) The end Q becomes:
- south pole
- north pole
- cannot say
- none of the above
(iii) The given bar shows magnetic properties only when …………… through the solenoid and it loses the magnetic properties as soon as the ……………
- current is switched off, current is switched on
- current is switched on, current is switched off
- current is switched on, current is switched on
- both (a) and (b)
The magnetic field of an electromagnet can be increased by …………… in the solenoid and by ……………through the solenoid.
- increasing the number of turns, decreasing the current.
- decreasing the number of turns, increasing the current.
- decreasing the number of turns, decreasing the current.
- increasing the number of turns, increasing the current.
The strength of an electromagnet can be increased by:
- reversing the directions of current
- using alternating current of high frequency
- increasing the current in the coil
- decreasing the number of turns of coil
A soft iron piece is in the form of a closed ring (no free ends). A wire is wound over it to make it an electromagnet. What happens when current is passed in the wire ?
- It does not get magnetised.
- It gets temporarily magnetised.
- It becomes magnetised.
- It can be magnetised if broken into two parts.