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Physics · 2025 · 3 marks
CBSE 2025 · Region 2 · Set 1 · Q24
(a) State Lenz's law. (b) In the given figure: (i) Identify the machine. (ii) Name the parts P and Q and R of the machine. (iii) Give the polarities…
(a)
State Lenz's law.
(b)
In the given figure:
(i)
Identify the machine.
(ii)
Name the parts P and Q and R of the machine.
(iii)
Give the polarities of the magnetic poles.
(iv)
Write the two ways of increasing the output voltage.
Marking-scheme solution
(a)
Lenz's law – The polarity of induced emf is such that it tends to produce a current which opposes the change in magnetic flux that produced it.
(b)(i)
AC generator
(ii)
P – Slip rings
Q – Carbon brushes
R – Armature coil
(iii)
Left side of the magnet is North & right side is South or vice-versa.
(iv)
By increasing the number of turns in the armature coil.
By increasing the speed of rotation of the armature coil.
By increasing the strength of the magnetic field B.
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