In a certain process, 400 cal of heat is supplied to a system and at the same time 105 J of mechanical work was done on the system. The increase in its internal energy is
20 cal
303 cal
404 cal
425 cal
A standing wave $y=A \sin \left(\frac{20}{3} \pi x\right) \cos (1000 \pi t)$ is maintained in a taught string, where $y$ and $x$ are in metres. The distance between two successive points oscillating with the amplitude $\frac{A}{2}$ across a node is
2.5 cm
25 cm
5 cm
10 cm
Two rods $P$ and $Q$ have equal lengths. Their thermal conductivities are $K_1$ and $K_2$ and cross-sectional areas are $A_1$ and $A_2$. When the temperature at ends of each rod are $T_1$ and $T_2$ respectively, the rate of flow of heat through $P$ and $Q$ will be equal, if
$\frac{A_1}{A_2}=\frac{K_2}{K_1}$
$\frac{A_1}{A_2}=\frac{K_2}{K_1} \times \frac{T_2}{T_1}$
$\frac{A_1}{A_2}=\sqrt{\frac{K_1}{K_2}}$
$\frac{A_1}{A_2}=\left(\frac{K_2}{K_1}\right)^2$
A bar magnet has magnetic moment of $0.05 \mathrm{Am}^2$ which is suspended in uniform magnetic field of 0.2 T . Calculate the work done in rotating the magnet from its most stable to most unstable position in the magnetic field.
0.05 J
0.10 J
0.15 J
0.20 J
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