A current flows in a wire, running between the S and N poles of a magnet lying horizontally as shown in the figure below:
The force on the wire due the magnet is directed.
From N to S
From S to N
Vertically downwards
Vertically upwards
(3)
Force on conductor is calculated using Fleming's left hand rule.
Which of the following is not true?
Induction proceeds attractions
We cannot isolate a single pole
We can magnetise an iron ring
A permanent magnet retains its magnetism even when heated on a flame
(4)
A permanent magnet does not loose its magnetism even when heated on a flame.
Which of the following combination is not correct?
Electric Motor — Fleming's right hand rule
Electric generator — Electromagnetic induction
Earth wire — Green colour
Compass Needle — Small Magnet
(1)
A electric motor works on the principle of Fleming's left hand rule.
By removing the inducing magnets, the induced magnetism is:
Finished after sometime
Finished just after
Non-finished for a long time
Not Charged
(2)
As induced magnetism takes place, as long as the induced magnet is present.
A copper wire is held between the poles of a magnet:
The current in the wire can be reversed. The pole of the magnet can also be changed over. In how many of the four directions shown can the force act on the wire?
1
2
3
4
(2)
By Fleming's left hand rule, we know that the force on the wire is perpendicular to the current in the wire and the magnetic field.
That it, there are only two possibilities for the direction of force i.e., upward or downward.
Commercial electric motors do not use:
An electromagnet to rotate the armature
Effectively large number of conducting wire in the current carrying coil
A permanent magnet to rotate the armature
A soft iron core on which the coil is wound
(3)
Using, electromagnet, the magnetic field strength further increase by, increasing the current. Hence, it will enhance the power of electric motor.
The device used for producing electric current is called a:
Generator
Galvanometer
Ammeter
Motor
(1)
A.C. generator is used to convert mechanical energy to electrical energy.
The essential difference between an A.C. generator and a D.C. generator is that:
A.C. generator has an electromagnet while a D.C. generator has permanent magnet.
D.C. generator will generate a higher voltage.
A.C. generator will generate a higher voltage.
A.C. generator has slip rings while the D.C. generator has a commutator.
(4)
Most essential difference between A.C. generator and D.C. generator is using slip ring in A.C. generator and commutator in D.C. generator.
At the time of short circuit, the current in the circuit:
Reduces substantially
Does not change
Increases heavily
Vary continuously
(3)
A short circuit occurs when circuit current rises rapidly and the electric circuit drown an heavy amount of current from the supply.
