Recent questions in Physics

A bulb connected to 50 V, DC consumes 20 W power. Then the bulb is connected to a capacitor in an a.c. power supply of 250 V, 50 Hz. Find the value of the capacitor required so that the bulb draws the same amount of current.

asked Mar 12, 2014 by balaji.thirumalai

1 answer

Calculate the mutual inductance between two coils when a current of 4 A changing to 8 A in 0.5 s in one coil, induces an emf of 50 mV in the other coil.

asked Mar 12, 2014 by balaji.thirumalai

1 answer

60 gm of ice at $\;-5^{0}C\;$ is mixed with 100 gm of water at $\;50^{0}C\;$ . Latent heat of fusion = 80 cal/g , Specific heat of water = $\;1 cal/g^{0}C\;$ ,Specific heat of ice = $\;0.5 cal/g^{0}C$ . Then the mass of ice left in the mixture = ?

asked Mar 12, 2014 by yamini.v

1 answer

100 g of ice at $\;0^{0}C\;$ is mixed with 100 g of water at $\;20^{0}C\;$ . Latent heat of fusion of fusion is 80 cal/g & specific heat of water is $\;1 cal /g^{0}C\;$ . The final temperature of mixture =

asked Mar 12, 2014 by yamini.v

1 answer

Consider a solenoid coil with $N= 10$ turns with radius $12 \times 10^{−2}m$ . The solenoid is subjected to a varying magnetic field that changes uniformly from $5 T \rightarrow 2 T$ in an interval of $12 s$ . The axis of the solenoid makes an angle of $13 ^{\circ}$ to the magnetic field. If the angle is changed to $67 ^{\circ}$ , what would the radius need to be for the emf to remain the same?

asked Mar 12, 2014 by balaji.thirumalai

1 answer

A circular coil of $N=5$ turns with radius $r=1.73 m$ is subjected to a varying magnetic field that changes uniformly from $2.18 T$ to $12.7 T$ in an interval of $180 \text{seconds}$ . The axis of the solenoid makes an angle of $27 ^{\circ}$ to the magnetic field. Find the induced emf.

asked Mar 12, 2014 by balaji.thirumalai

1 answer

An aircraft having a wingspan of $20.48\; m$ flies due north at aspeed of $40 ms^{−1}$ . If the vertical component of earth’s magneticfield at the place is $2 × 10^{−5}\; T$ , Calculate the emf induced betweenthe ends of the wings.

asked Mar 12, 2014 by balaji.thirumalai

1 answer

Three conducting rods of same material & area of cross - section are figured as shown . Then , $\;\large\frac{l_{1}}{l_{2}}=?$

asked Mar 12, 2014 by yamini.v

1 answer

The figure expansion of an ideal gas through two processes A & B . Let $\;\bigtriangleup Q_{A}\;$ & $\;\bigtriangleup Q_{B}\;$ be the heat given to the system in processes A & B respectively . Then

asked Mar 12, 2014 by yamini.v

1 answer

The first law of thermodynamics following from

asked Mar 12, 2014 by yamini.v

1 answer

A heat engine operates between a cold reservoir at temperature $\;T_{2}=600 K\;$ & a hot reservoir at temperature $\;T_{1}\;.$ It takes 1000 J of energy from hot reservoir & gives 200 J . What can be the minimum temperature of the hot reservoir

asked Mar 12, 2014 by yamini.v

1 answer

A heat engine operates between a cold reservoir at temperature $\;T_{1}=300 K\;$ & a hot reservoir at temperature $\;T_{2}=600 K\;$ . It takes 500 J heat from hot reservoir and delivers x J of heat to cold reservoir in a cycle . Then x = ?

asked Mar 12, 2014 by yamini.v

1 answer

An engine intakes 10 g of steam per sec at $\;100^{0}C\;$ & cools it down to $\;50^{0}C\;$ . ( latent heat of vapourization of steam = 540 $\;calg^{-1}$ ) Heat rejected by engine per minute

asked Mar 12, 2014 by yamini.v

1 answer

An ideal gas is made to expand isothermally from $\;V_{1}\;$ to $\;V_{2}\;$ & is then compressed adiabatically to $\;V_{1}\;$ . Then the total work done is -

asked Mar 12, 2014 by yamini.v

1 answer

A ball is dropped from a height of $10\; m$ & it rises to a height of $5\; m$ . Assuming $\;50 \%\;$ of the energy goes into increasing temperature of ball , the temperature rise is (specific heat of ball's material = $\;1000 JK^{-1}$ )

asked Mar 12, 2014 by yamini.v

1 answer

If heat is supplied to a solid , its temperature -

asked Mar 12, 2014 by yamini.v

1 answer

Two balls of equal masses moving with $\;10 \;ms^{-1}\;$ towards each other collide after some time . Considering the collision to be inelastic & mass of each ball to be 1 kg , the thermal energy developed in the process is equal to what?

asked Mar 12, 2014 by yamini.v

1 answer

A vehicle (mass=1000 kg) , moving at a speed of $\;36 \;kmh^{-1}\;$ is stopped in 2 s . Assuming that $\;50 \%\;$ of the mechanical energy lost appears as thermal energy , the average rate of production of thermal energy in $\;cal s^{-1}\;$ is -

asked Mar 12, 2014 by yamini.v

1 answer

When a hot liquid sample is mixed with a cold one , the temperature of the mixture

asked Mar 12, 2014 by yamini.v

1 answer

A calorimeter (water equivalent = 25 g ) contains of 265 g of water at $\;30^{0}C\;$ . Steam is passed at $\;100^{0}C\;$ is passed which increases the temperature to $\;40^{0}C\;$ & the mass of the calorimeter and its contents by 2g . Given that the specific heat capacity of water is $\;1\;{calg^{-1}}^{0}C\;$ , the latent heat of vapourization of water is -

asked Mar 12, 2014 by yamini.v

1 answer

A bullet is fired into a box & penetrates it . The penetration process melts it . Assuming that $\;25 \%\;$ of its K.E . goes in heating & the initial and final temperature are $\;27^{0}C\;$ & $\;327^{0}C\;$ , the initial velocity is - (specific heat capacity = $\;100 Jkg^{-1}K^{-1}\;$ Latent heat of fusion = $\;2 \times 10^{4} Jkg^{-1}$ )

asked Mar 12, 2014 by yamini.v

1 answer

A ball is dropped from a height of 1000 Km .Due to heat from air friction & melts just before reaching the ground . The latent heat of fusion of ball's material is - (specific heat of material =100 $\;{J kg^{-1}}^{0}C$ Air tempeature= $\;25^{0}C\;$ , Melting point = $\;{J kg^{-1}}^{0}C\;$ )

asked Mar 12, 2014 by yamini.v

1 answer

The mechanical equivalent of heat -

asked Mar 12, 2014 by yamini.v

1 answer

As the temperature increases , the time period of the pendulum -

asked Mar 12, 2014 by yamini.v

1 answer

A circular coil of area $0.04 m^2$ , 200 turns and resistance 2 $\Omega$ changes from $0.1 \;Wb \;m^{−2}$ to $0.04 \;Wb\; m^{−2}$ in $0.02 \text{seconds}$ . Find the induced emf.

asked Mar 12, 2014 by balaji.thirumalai

1 answer

From a rectangular box , a circular portion is removed and the figure looks like - when the object is heated , the distance PQ -

asked Mar 12, 2014 by yamini.v

1 answer

Ram is pedaling his bicylce down a road, perpendicular to the Earth's magnetic field of $5.5 \times 10^{-5} T$ . His Wheel has an area of $1.2 m^2$ . What is the flux through the metal rim of his bicycle wheel?

asked Mar 12, 2014 by balaji.thirumalai

1 answer

A pendulum clock is made of iron rod $\;(\alpha_{iron}={10^{-5}}^{0}C^{-1})\;.$ At room temperature $\;(15^{0}C)\;,$ it works correctly . The error when the temperature rises to $\;24^{0}C\;$

asked Mar 12, 2014 by yamini.v

1 answer

A pendulum clock having copper rod keeps correct at $\;20^{0} C\;.$ It gains 15 seconds per day if cooled to $\;0^{0}C\;.$ Calculate the coefficient of linear expansion of copper :

asked Mar 12, 2014 by yamini.v

1 answer

If ideal gas is taken through a process given by the graph below, identify which of the following options is incorrect:

asked Mar 11, 2014 by balaji.thirumalai

1 answer

If the plot of density $\rho$ versus temperature $T$ is as given below, identify which of the following statements is incorrect?

asked Mar 11, 2014 by balaji.thirumalai

1 answer

Q Joules of Heat is given to a sample of Helium in such a manner that the pressure remains constant throughout. The work done by the gas is then?

asked Mar 11, 2014 by balaji.thirumalai

1 answer

The equation of a state of gas is given by $PV = nRT + Pb$ . If the gas is isothermally expanded from a volume $V$ to $2V$ , what is the work done during the process?

asked Mar 11, 2014 by balaji.thirumalai

1 answer

The density of the gaseous mixture of Hydrogen and Carbon-di-Oxide is $\large\frac{30\;g}{22.4\;l}$ at NTP. What is the % composition of Hydrogen and Carbon-di-oxide by volume in the mixture respectively?

asked Mar 11, 2014 by balaji.thirumalai

1 answer

A student while performing an experiment forgot to add the reaction mixture and started heating the open round bottom flask on the flame. If he found the temperature to be $227 ^{\circ} C$ after heating, which was $27 ^{\circ} C$ earlier, what fraction of air would have been expelled out?

asked Mar 11, 2014 by balaji.thirumalai

1 answer

A gaseous compound X contains 44.4% Carbon, 51.9% Nitrogen and 3.7% Hydrogen. Under like conditions, same volume of X as that of Hydrogen took 50 seconds to diffuse whereas Hydrogen took 9.62 seconds. What is the molecular formula of X?

asked Mar 11, 2014 by balaji.thirumalai

1 answer

Consider a gas in a container which is made air tight. Now, there is a movable piston fitted with the container. The gas performs some mechanical work on the piston by moving it. The reason the gas performs its work is because of which of the following?

asked Mar 11, 2014 by balaji.thirumalai

1 answer

2 Moles of Oxygen is heated from $0 ^{\circ} C$ at constant pressure till its volume increases by $20%$ . The specific heat of Oxygen is given to be $0.22$ cal $\;g^{-1} K^{-1}$ . What is the amount of heat required?

asked Mar 11, 2014 by balaji.thirumalai

1 answer

For an ideal gas, the following conversions are made:

asked Mar 11, 2014 by balaji.thirumalai

1 answer

An ideal gas has a molar heat capacity pressure $C_p = 2.5 R$ . The gas is kept in a closed volume of $0.083 m^3$ at a temperature of $300 ^{\circ}K$ and a pressure of $10^5 N/m^2$ . $200J$ of heat is supplied to the gas. Calculate the final temperature and pressure of the gas.

asked Mar 11, 2014 by balaji.thirumalai

1 answer

Two gases are sent through 2 ends of a 2m long pipe. If the gases reach at a distance of 1.5m from the end of the lighter gas, then what is the ratio of their masses (lighter: heavier), assuming pressure conditions to be the same?

asked Mar 11, 2014 by balaji.thirumalai

1 answer

In the figure below, $N_2$ and $H_2$ are sent into the metre pipe through the two ends. At what distance $x$ will Ammonia be formed.

asked Mar 11, 2014 by balaji.thirumalai

1 answer

If N molecules of $O_2$ at $- 73^{\circ}$ possess the same kinetic energy as another sample of $H_2$ at $27^{\circ}$ then the number of molecules of $H_2$ is ?

asked Mar 11, 2014 by balaji.thirumalai

1 answer

What would be the most likely value for C $_T$ , the molar heat capacity at constant temperature?

asked Mar 11, 2014 by balaji.thirumalai

1 answer

An open vessel containing 3 moles of an ideal gas at $300 ^{\circ}$ is heated to $500 ^{\circ}$ . What is the number of moles left after heating?

asked Mar 11, 2014 by balaji.thirumalai

1 answer

When an open vessel is heated, which of the following holds true for the ideal gas inside the vessel?

asked Mar 11, 2014 by balaji.thirumalai

1 answer

A proton is bombarded on a stationary lithium nucleus. As a result of collision two $\;\alpha\;$ particles are produced . If direction of motion of $\;\alpha \;$ particle with initial direction of motion makes an angle $\;cos^{-1}(\large\frac{1}{4})\;$ find kinetic energy of striking proton . Given binding energies per nucleon of $\;Li^{7}\;$ & $\;He^{4}\;$ are $5.60 MeV$ and $7.06 MeV$ respectively

asked Mar 11, 2014 by yamini.v

1 answer

The half life of $\;^{215}At\;$ is $\;200 \mu s\;$ . The time taken for radioactivity of a sample of $\;^{215}At\;$ to decay to $\;{\large\frac{1}{4}}^{th}\;$ of its initial value is

asked Mar 11, 2014 by yamini.v

1 answer

Two wave pulse A & B are moving in opposite directions .along a taut string with a speed of 2.00 cm/sec . The amplitude of A is twice the amplitude of B . The pulse are shown in figure given at t=0 .Which is string shape of string at t=3 sec ?

asked Mar 11, 2014 by yamini.v

1 answer

The angular frequency 'w' of the system is

asked Mar 11, 2014 by yamini.v

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