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❓ Important Questions
यह page magnetic field, rules, force, motor, electromagnetic
induction और generator के important conceptual और competency-based
questions को cover करता है।
Section A – Very Short Answer
Q1
What is a magnetic field?
The region around a magnet or current-carrying conductor
where magnetic force can be detected is called a magnetic field.
Q2
What are magnetic field lines?
They are imaginary lines used to represent the direction
and relative strength of a magnetic field.
Q3
State the right-hand thumb rule.
Thumb shows the direction of current and curled fingers
show the direction of magnetic field around a straight conductor.
Q4
What is an electromagnet?
An electromagnet is a temporary magnet produced by passing
current through a suitable coil, often with a soft iron core.
Q5
What is electromagnetic induction?
It is the phenomenon of inducing current in a conductor due
to changing magnetic conditions associated with it.
Q6
Name the rule used to find the force direction on a current-carrying conductor.
Fleming's Left Hand Rule.
Section B – Short Answer
Q7
Why do magnetic field lines never intersect each other?
At a given point the magnetic field has a unique direction.
If field lines crossed, the field would have two directions
at the same point.
Q8
What happens to the magnetic field around a straight conductor
when current is increased?
The magnetic field becomes stronger.
Q9
Why does a solenoid behave like a bar magnet?
The magnetic fields produced by its many current-carrying
turns combine to produce a field pattern with distinct
north-like and south-like ends.
Q10
How can the strength of an electromagnet be increased?
Increase current, increase the number of turns per unit length,
and use a suitable soft iron core.
Q11
When is force on a current-carrying conductor in a magnetic
field maximum?
The force is maximum when the conductor is perpendicular
to the magnetic field.
Q12
What is the function of the split-ring commutator in a DC motor?
It reverses the current through the coil after each half turn
so that the coil continues rotating in the same sense.
Section C – Reasoning Questions
Q13
Why does a current-carrying wire behave like a magnet?
Because electric current produces a magnetic field around
the conductor.
Q14
Why are magnetic field lines more crowded near the poles
of a bar magnet?
Closer field lines represent a stronger magnetic field,
and the field is strongest near the poles.
Q15
Why does an induced current disappear when the magnet and
coil stop moving relative to each other?
Because there is no continuing change in the magnetic
conditions linked with the coil.
Q16
Why does a motor rotate when current flows through its coil?
Opposite sides of the current-carrying coil experience
magnetic forces in opposite directions, producing a turning effect.
Section D – Diagram-Based Questions
Q17
Draw magnetic field lines around a straight current-carrying conductor.
Draw concentric circles centred on the conductor and mark
their direction using the right-hand thumb rule.
Q18
Draw the magnetic field pattern of a solenoid.
Show nearly parallel field lines inside the solenoid and
the return field outside.
Q19
Draw and label an electric motor.
Label coil/armature, magnet, split ring, brushes and battery.
Q20
Draw a simple electric generator diagram.
Show rotating coil, magnetic field, brushes and the
appropriate ring arrangement.
Section E – Long Answer
Q21
Explain the magnetic field produced by a current-carrying
straight conductor.
Explain concentric field lines, direction using right-hand
thumb rule, effect of current and effect of distance.
Q22
Explain the construction and working of an electric motor.
Write principle, components, magnetic force on coil,
turning effect and role of split-ring commutator.
Q23
Explain electromagnetic induction and the working of
an electric generator.
Describe changing magnetic conditions, induced current,
rotation of coil and conversion of mechanical energy into
electrical energy.
Q24
Compare Fleming's Left Hand Rule and Right Hand Rule.
Left Hand Rule is associated with motor effect and force.
Right Hand Rule is used for direction of induced current
in generator/induction situations.
Section F – Competency / Application
Q25
A current-carrying wire is placed in a magnetic field.
The wire experiences no force when the wire is parallel
to the field. Explain why.
For F = BIL sin θ, when the wire is parallel to the field,
θ = 0° and sin 0° = 0, so the force is zero.
Q26
A student increases the current in an electromagnet.
What change in magnetic field strength is expected?
The magnetic field becomes stronger.
Q27
A magnet is moved rapidly into a coil. Why is the induced
effect stronger than when it is moved slowly?
Rapid motion produces a faster change in the magnetic
conditions associated with the coil, resulting in a
larger induced effect.
Q28
What happens if the direction of current in a motor coil
is reversed while the magnetic field direction remains unchanged?
The direction of force on the conductor reverses, so the
tendency of the motor coil to rotate reverses.
⚡ Final Exam Focus
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Right-hand thumb rule
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Magnetic field of straight conductor
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Circular loop and solenoid
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Force on current-carrying conductor
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Fleming's Left Hand Rule
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Electromagnetic induction
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Fleming's Right Hand Rule
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Electric motor and generator