2 Marks Questions

Question 12 Marks

Sunita and her friends went to an exhibition. The guard standing there asked them to pass through a metal detector. Sunita's friends were first afraid but when Sunita told them the reason and explain its working.
Answer the following questions :
(a) State the principle on which metal detector works.
(b) If a person passing through metal detector has some metallic object then why does it produces sound?
(c) Tell two qualities of Sunita which she showed while explaining the reason for passing through it.

Answer

(a) Metal detector works on the principle of resonance in ac circuit.
(b) Impedance of the circuit changes and as a result, resultant current in the circuit changes and this is the reason that the metal detector produces sound.
(c) (i) Knowledge, (ii) scientific temper.

View full question & answer→

Question 22 Marks

When a capacitor is joined with a series LR circuit in series, then current flowing through the circuit increases. Explain, why?

Answer

Impedance of L-R circuit
$ Z_1=\sqrt{R^2+(\rho L)^2} \quad
\therefore \text { Current } I_1=\frac{E}{Z_1} $
On joining capacitor, impedance of LCR circuit
$Z _2=\sqrt{ R ^2+\left(\omega L -\frac{1}{\omega C }\right)^2} \therefore$ Current $I _2=\frac{ E }{ Z _2}$
$\therefore \quad \frac{ I _2}{ I _1}=\frac{ Z _1}{ Z _2}$
Since, $Z_1>Z_2$ Hence $\quad I _2> I _1$

View full question & answer→

Question 32 Marks

Explain the root mean square value of alternating current.

Answer

Root mean square value : The square root of the mean square of the instantaneous value of alternating curent is called the root mean square value $I_{\text {rms }}$ of the current. Root mean square value of alternating current is equal to the magnitude of direct current which shows the same heating effect as shown by alternating current. It is denoted by $I _{ rms }$.
$I _{ rms }=\frac{ I _0}{\sqrt{2}}$
$I _{ rms }=0.707 I _0$
It is clear from expression (1) that root mean square value of alternating current is $70.7 \%$ of its peak value.

View full question & answer→

Physics 2 Marks Questions

Test yourself on this topic