The thermo emf of a hypothetical thermocouple varies with the temperature \(\theta\) of the hot junction as \(E=a\theta+b\theta^2\) in volts, where the ratio is \(\frac ab\) is \(700~^\circ \mathrm{C}.\) If the cold junction is kept at \(0~^\circ \mathrm{C},\) then the neutral temperature is:
1. | \(700~^\circ \mathrm{C}\) |
2. | \(1400~^\circ \mathrm{C}\) |
3. | \(-350~^\circ \mathrm{C}\) |
4. | No neutral temperature is possible for this thermocouple. |
A launching vehicle carrying an artificial satellite of mass \(m\) is set for launch on the surface of the earth of mass \(M\) and radius \(R.\) If the satellite is intended to move in a circular orbit of radius \(7R,\) the minimum energy required to be spent by the launching vehicle on the satellite is:
(Gravitational constant= \(G\))
1. \(\frac{GMm}{R}\)
2. \(-\frac{13GMm}{14R}\)
3. \(\frac{GMm}{7R}\)
4. \(-\frac{GMm}{14R}\)
If the ratio of lengths, radii and Young's modulus of steel and brass wires shown in the figure are \(a,\) \(b\) and \(c\) respectively, the ratio between the increase in lengths of brass and steel wires would be:
1. \( \frac{{b}^{2}a}{2c}\)
2. \( \frac{bc}{2{a}^{3}}\)
3. \( \frac{{ba}^{2}}{2c}\)
4. \( \frac{a}{2{b}^{2}c}\)
A soap bubble of radius \(r\) is blown up to form a bubble of radius \(2r\) under isothermal conditions. If \(T\) is the surface tension of the soap solution, the energy spent in the blowing is:
1. \(3\pi Tr^2\)
2. \(6\pi Tr^2\)
3. \(12\pi Tr^2\)
4. \(24\pi Tr^2\)
A current of \(1.6\) A is passed through a solution of CuSO4. How many Cu++ ions are liberated in one minute? (Electronic charge= \(1.6\times10^{-19}\) C)
1. 3 × 1020
2. 3 × 1010
3. 6 × 1020
4. 6 × 1010
1. | a magnet |
2. | an unmagnetised iron bar |
3. | a moving charge |
4. | stationary charge |
1. | they travel with the speed of sound. |
2. | the frequency is not constant. |
3. | they can, heavily absorbed by the atmosphere. |
4. | the height of antenna has to be increased several times. |