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Science · 2022 · 3 marks
CBSE 2022 · Region 3 · Set 1 · Q12
(a) In the diagram given below, Coil - 1 is connected in series with a battery and a plug key while Coil - 2 is connected with a galvanometer. (i)…
(a)
In the diagram given below, Coil - $\displaystyle 1$ is connected in series with a battery and a plug key while Coil - $\displaystyle 2$ is connected with a galvanometer.
(i)
Why does the galvanometer show deflection only when the key (K) is plugged in and not when a steady current starts flowing in the circuit ?
(ii)
What is observed in the galvanometer, when the key is plugged out ?
(iii)
State the conclusion based on the observation of this activity.
(b)
In the figure given below, a simple electric motor is shown :
As shown in the figure, the current in the coil $\displaystyle A B C D$ flows from $\displaystyle A$ to $\displaystyle B$ in the arm $\displaystyle A B$ and $\displaystyle C$ to $\displaystyle D$ in the arm $\displaystyle C D$.
(i)
State the directions in which the arms AB and CD will experience a force.
(ii)
Identify the part of the electric motor that reverses the flow of current in the coil ABCD and write its name.
(iii)
After the reversal of flow of current in the coil ABCD, state the directions in which the arms AB and CD will experience a force.
(iv)
Name the rule which is applied to determine the direction of force on a current carrying conductor placed in a magnetic field.
Marking-scheme solution
(a)
(i) • When the key is plugged-in, current starts in coil-$\displaystyle 1$, the magnetic field around the coil is changed. This produces induced current in the coil - $\displaystyle 2$ and galvanometer shows deflection
There is no change in magnetic field when a steady current starts flowing in the circuit.
(ii) Galvanometer shows deflection in the opposite direction.
(iii) Conclusion: Induced current is produced only when there is a change in magnetic field which occurs only when the key is plugged in or plugged out.
(b)
(i) \(\displaystyle \operatorname{Arm} A B\)-Downward, Arm \(\displaystyle C D\)-Upward
(ii) \(\displaystyle P\) and \(\displaystyle Q\)-Split ring / Commutator
(iii) Arm \(\displaystyle A B\) upward, Arm CD downward/Direction of force will get reversed
(iv) Fleming's left-hand rule
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CBSE Class 10 Science past-paper question from the 2022 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.