The angle of dip increases as we move from ————–
a) Equator to poles b) Poles to equator c) Dip is equal at all places d) None of these Solution:... View Article
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How many photons are emitted per second by a 5 mW laser source operating at 632.8 nm?
Solution: The energy of a photon is given by the formula: E=\frac{hc}{\lambda} =\frac{(6.62*10^{-34})(3*10^{8})}{632.8*10^{-9}} = 3.14*10^{-19}J The energy emitted per second... View Article
In a mechanical refrigerator, the low temperature coils are at a temperature of −23 degree C and the compressed gas in the condenser has a temperature of 27 degree C. What is the theoretical coefficient of performance?
Solution: Given: Temperature of coil T_{2}=250K Temperature of condenser T_{1}=300K coefficient of performance of refrigerator = \frac{T_{2}}{T_{1}-T_{2}} = \frac{250}{300-250} =... View Article
The capacity of an isolated conducting sphere of radius R is proportional to
a) 2R b) R c) R^{2} d) 1/R Solution: b) R. Explanation: Since, C=4\pi \varepsilon _{0}R C\propto R
A book leans against a crate on a table. Neither is moving. Which of the following statements concerning this situation is correct?
a) The direction of the frictional force acting on the book is in the same direction as the frictional force... View Article
An object of mass 3m initially at rest splits into three equal fragments, Two fragments have velocities vhat{i} and vhat{j}. What is the velocity of the third fragment?
Solution: Initial momentum of 3m mass = 0 When the object of mass 3m splits into three fragments of equal... View Article
The process of heat transfer in which heat is transferred with actual migration of medium particles is known as
The process of heat transfer in which heat is transferred with actual migration of medium particles is known as convection.... View Article
A vehicle is moving with a velocity v on a curved road of width b and radius of curvature R. For counteracting the centrifugal force on the vehicle, the difference in elevation required in between the outer and inner edges of the road is?
a) \(\begin{array}{l}\frac{bv}{Rg}\end{array} \) b) \(\begin{array}{l}\frac{vb^{2}}{Rg}\end{array} \) c) \(\begin{array}{l}\frac{bv^{2}}{Rg}\end{array} \) d) \(\begin{array}{l}\frac{Rg^{2}}{bv}\end{array} \) Solution: c) \(\begin{array}{l}\frac{bv^{2}}{Rg}\end{array} \)
A spherical drop of capacitance 1 μF is broken into 8 drops of equal radius. What is the capacitance of each small drop?
Answer: Potential of a charged sphere is calculated using the below formula: \(\begin{array}{l}V=\frac{kQ}{R} \end{array} \). We know that Q =... View Article
A wheel whose moment of inertia is 12 kg m^2 has an initial angular velocity of 40 rad/s. A constant torque of 20 Nm acts on the wheel. The time in which the wheel is accelerated to 100 rad/s is
Solution: \(\begin{array}{l}T=I\alpha\end{array} \) \(\begin{array}{l}20=12*\alpha\end{array} \) \(\begin{array}{l}\alpha =\frac{20}{12}\end{array} \) \(\begin{array}{l}\omega_{0}=40\end{array} \) \(\begin{array}{l}\omega =\omega_{0}+\alpha t\end{array} \) \(\begin{array}{l}100 =40+\frac{20}{12}t\end{array} \) \(\begin{array}{l}\frac{60*12}{20}=t\end{array} \) t=36... View Article
A galvanometer has current range of 15mA and voltage range 750mV. To convert this galvanometer into an ammeter of range 25A, What is the required shunt?
Solution: \(\begin{array}{l}a=\frac{y}{I_{g}}\end{array} \) \(\begin{array}{l}=\frac{750*10^{-3}}{15*10^{-3}}\end{array} \) \(\begin{array}{l}=50\Omega \end{array} \) \(\begin{array}{l}I_{g}=\frac{S}{S+a}I\end{array} \) \(\begin{array}{l}15*10^{-3}=\frac{S}{S+50}*25\end{array} \) \(\begin{array}{l}=0.03\Omega\end{array} \)
A loudspeaker that produces signals from 50 to 500 Hz is placed at the open end of a closed tube of length 1.1 m. What are the lowest and the highest frequencies that excite resonance?
Solution: For closed tube f_{n}=\frac{nv}{4L} L=1.1m, v=330m/s f_{n}=\frac{n*330}{4*1.1} For highest frequency, f_{h}=\frac{6*330}{4*1.1} = 450 Hz For lowest frequency, f_{1}=\frac{1*330}{4*1.1} =... View Article
A right-angled triangle abc, made from a metallic wire, moves at a uniform speed v in its plane as shown in the figure. A uniform magnetic field B exists in the perpendicular direction. Find the emf induced (a) in the loop abc, (b) in the segment bc, (c) in the segment ac, and (d) in the segment ab.
Solution: (a) The emf induced in the loop abc is zero. Since the components of ab are opposite to of... View Article
A particle gets displaced by vec{Delta r}=(2hat{i}+3hat{j}+4hat{k})m under the action of a force vec{F}=(7hat{i}+4hat{j}+3hat{k}). The change in its kinetic energy is
Solution: \(\begin{array}{l}\vec{F}. \vec{\Delta r}=(7\hat{i}+4\hat{j}+3\hat{k}). (2\hat{i}+3\hat{j}+4\hat{k})\end{array} \) = 14+12+12=38J
Calculate the inductance of a unit length of a double tape line as shown in figure. The tapes are separated by a distance h which is considerably less than their width b.
Solution: \(\begin{array}{l}\oint \vec{B } . \vec{dl}= \mu _{0}I\Rightarrow B.2b= \mu _{0}I\end{array} \) \(\begin{array}{l}B=\frac{\mu_{0} I}{2b}\end{array} \) Net field = 2B Magnetic... View Article
A magnet is taken towards a conducting ring in such a way that a constant current of 10mA is induced in it. The total resistance of the ring is 0.5Ω. In 5s, the magnetic flux through the ring changes by?
Solution: \(\begin{array}{l}\Delta q \frac{\Delta \phi }{R}\end{array} \) \(\begin{array}{l} i\Delta t = \frac{\Delta \phi }{R}\end{array} \) \(\begin{array}{l}\Delta \phi = i(\Delta t)R\end{array}... View Article
A paramagnetic liquid is taken in a U-tube and arranged so that one of its limbs is kept between pole pieces of the magnet. What happens to the liquid level in the limb?
a) Remains the same b) Becomes empty c) Rises up d) Goes down Solution: c) Rises up
Consider a rod of weight W that is supported by two parallel knife edges A and B and is in equilibrium in a horizontal position. The knives are at a distance d from each other. The centre of mass of the rod is at distance x from A. The normal reaction on A is?
Solution: Taking moment about point B N_{A}d=W(d-x)=0 N_{A}=\frac{W(d-x)}{d}
If cabin is decending vertically with acceleration a and action by mass M on floor of cabin is 9Mg/10 then a equals to:
a) g b) g/10 c) (9/10) g d) (10/9) g Answer: b) g/10 Solution: Given. R = 9Mg/10 The cabin is... View Article
The pull P is just sufficient to keep the block of weight 14 N in equilibrium as shown. Pulleys are ideal. Find the value of P
a) 4 N b) 6 N c) 8 N d) 2 N Answer: d) 2 N Solution: Now if we consider... View Article
