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Science · 2026 · 5 marks
CBSE 2026 · Region 5 · Set 3 · Q39
(A) (i) State the rule which gives the direction of force acting on a current carrying conductor placed in a uniform magnetic field. (ii) Name any…
(i)
State the rule which gives the direction of force acting on a current carrying conductor placed in a uniform magnetic field.
(ii)
Name any two devices which work on the basis of an interaction between magnetic field and current carrying conductor.
(iii)
Observe the given diagrams :
Comment on the magnitude of force on electron in both the cases and give reason for your answer.
(i)
List three possible reasons of short-circuiting in an electric circuit.
(ii)
In case of overload, will the fuse protect to given electric circuit from damage ? Justify your answer.
(iii)
For an electric heater rated as $\displaystyle 220$ V, $\displaystyle 2200$ W, what should be the minimum rating of fuse used with it ?
Marking-scheme solution
(i)
Stretch the thumb, forefinger and middle finger of your left hand such that they are mutually perpendicular. If the first finger points in the direction of magnetic field and the second finger in the direction of current, then the thumb will point in the direction of motion or the force acting on the conductor.
(ii)
Electric motor, loud speaker, electric generator, microphones, measuring instruments.
(iii)
For fig (I)
Maximum force
Because direction of motion of electron is perpendicular to the direction of magnetic field.
For fig (II)
Zero/ No force
Because direction of magnetic field and direction of movement of electron are same.
(i)
Direct contact between live and neutral wire
Insulation of electrical wires is damaged.
Overloading
(ii)
No,
The fuse must be connected in series with live wire.
(iii)
$\displaystyle \mathrm{P}=\mathrm{VI} \quad \mathrm{I}=\frac{2200}{220}=10 \mathrm{~A}$
The minimum rating of the fuse should be slightly more than $\displaystyle 10$ A.
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CBSE Class 10 Science past-paper question from the 2026 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.