\(X\) different wavelengths may be observed in the spectrum from a hydrogen sample if the atoms are exited to states with principal quantum number \({n}=6\) ? The value of \({X}\) is ..... .

The arm \(P Q\) of a rectangular conductor is moving from \(x=0\) to \(x=2 b\) outwards and then inwards from \(x=2 b\) to \(x=0\) as shown in the figure. A uniform magnetic field perpendicular to the plane is acting from \(x=0\) to \(x=b\). Identify the graph showing the variation of different quantities with distance.

In a car race on straight road, car \(A\) takes a time \(t\) less than car \(B\) at the finish and passes finishing point with a speed \(v\) more than that of car \(B.\) Both the cars start from rest and travel with constant acceleration \(a_1\) and \(a_2\) respectively. Then \(v\) is equal to

12 wires each having resistance \(2 \Omega\) are joined to form a cube. A battery of \(6 \mathrm{~V}\) emf is joined across point \(\mathrm{a}\) and \(\mathrm{c}\). The voltage difference between \(e\) and \(f\) is ______V.

Which one of the following forces cannot be expressed in terms of potential energy?

A bullet looses \({\left( {\frac{1}{n}} \right)^{th}}\) of its velocity passing through one plank. The number of such planks that are required to stop the bullet can be

Speed of an electron in Bohr's \(7^{\text {th }}\) orbit for Hydrogen atom is \(3.6 \times 10^6\,m / s\). The corresponding speed of the electron in \(3^{\text {rd }}\) orbit, in \(m / s\) is \(........\times 10^6\)

\(64\) identical drops each charged upto potential of \(10\,mV\) are combined to form a bigger dorp. The potential of the bigger drop will be \(..........\,mV\)

The density \(\rho\) of a uniform cylinder is determined by measuring its mass \(m\), length \(l\) and diameter \(d\). The measured values of \(m\), \(l\) and \(d\) are \(97.42 \pm 0.02\) g, \(8.35 \pm 0.05\) mm and \(20.20 \pm 0.02\) mm, respectively. Calculated percentage fractional error in \(\rho\) is _______.

The value of current I in the electrical circuit as given below, when potential at A is equal to the potential at B, will be ____ A.

A \(2\,V\) battery is connected across \(AB\) as shown in the figure. The value of the current supplied by the battery when in one case battery's positive terminal is connected to \(A\) and in other case when positive terminal of battery is connected to \(B\) will respectively be