$A$ source of sound is travelling with a velocity of $40\, km/h$ towards an observer and emits sound of frequency $2000\, Hz$. If the velocity of sound is $1220\, km/h$,what is the apparent frequency heard by the observer in $Hz$?

Two dice are rolled simultaneously. The probability that the sum of the two numbers on the dice is a prime number is:

The lungs are covered by which of the following?

Assertion $(A)$: $A$ current of $96.5 \ A$ is passed into aqueous $AgNO_3$ solution for $100 \ s$. The weight of silver deposited is $10.8 \ g$ (At. wt. of $Ag = 108$).
Reason $(R)$: The mass of a substance deposited during the electrolysis of an electrolyte is inversely proportional to the quantity of electricity passing through the electrolyte.
The correct answer is:

$A$ galvanometer,having a resistance of $50 \Omega$,gives a full-scale deflection for a current of $0.05 \text{ A}$. The length in metres of a resistance wire of cross-sectional area $2.97 \times 10^{-2} \text{ cm}^2$ that can be used to convert the galvanometer into an ammeter which can read a maximum of $5 \text{ A}$ current is: (Specific resistance of the wire $= 5 \times 10^{-7} \Omega\text{-m}$)

Degenerate electron pressure will not be sufficient to prevent core collapse of a white dwarf if its mass becomes $n$ times the solar mass. The value of $n$ is: