In an experment ot verify Newton's law of cooling, a graph is plotted between, the temperature difference \((\Delta T )\) of the water and surroundings and time as shown in figure. The initial temperature of water is taken as \(80^{\circ} \,C\). The value of \(t _{2}\) as mentioned in the graph will be...........

Energy of \(10\) non rigid diatomic molecules at temperature \(\mathrm{T}\) is _______.

A train is moving on a straight track with speed \(20\ ms^{-1}\). It is blowing its whistle at the frequency of \(1000\ Hz\). The percentage change in the frequency heard by a person standing near the track as the train passes him is ( speed of sound \(=320\) \(ms^{-1}\) ) close to .... \(\%\)

Three Carnot engines operate in series between a heat source at a temperature \(T_1\) and a heat sink at temperature \(T_4\) (see figure). There are two other reservoirs at temperature \(T_2\) and \(T_3\), as shown, with \(T_1 > T_2 > T_3 > T_4\). The three engines are equally efficient if

Consider a \(72\, cm\) long wire \(AB\) as shown in the figure. The galvanometer jockey is placed at \(P\) on \(A B\) at a distance \(x cm\) from \(A\). The galvanometer shows zero deflection. The value of \(x,\) to the nearest integer, is ..... \(cm\)

A rigid square loop of side \(a\) and carrying current \(I_2\) is laying on a horizontal surface near a long current \(I_1\) wire in the same plane as shown in figure. The net force on the loop due to the wire will be

A student measuring the diameter of a pencil of circular cross-section with the help of a vernier scale records the following four readings \(5.50\, mm , 5.55\, mm ,\)\( 5.45\, mm ; 5.65\, mm .\) The average of these four readings is \(5.5375\, mm\) and the standard deviation of the data is \(0.07395\, mm .\) The average diameter of the pencil should therefore be recorded as

Two polarisers \(P_1\) and \(P_2\) are placed in such a way that the intensity of the transmitted light will be zero. A third polariser \(P_3\) is inserted in between \(P_1\) and \(\mathrm{P}_2\), at the particular angle between \(\mathrm{P}_2\) and \(\mathrm{P}_3\). The transmitted intensity of the light passing the through all three polarisers is maximum. The angle between the polarisers \(\mathrm{P}_2\) and \(\mathrm{P}_3\) is :

Under isothermal condition, the pressure of a gas is given by \(P = aV ^{-3}\), where \(a\) is a constant and \(V\) is the volume of the gas. The bulk modulus at constant temperature is equal to \(..........\,P\)

A radioactive substance decays to \(\left(\frac{1}{16}\right)^{t h}\) of its initial activity in \(80\, days.\) The half life of the radioactive substance expressed in days is ... .

The transfer characteristic curve of a transistor, having input and output resistance \(100\,\Omega \) and \(100\,k\Omega \) respectively, is shown in the figure. The Voltage and Power gain, are respectively