The temperature inside a refrigerator is t2 ºC and the room temperature is t1 ºC. The amount of heat delivered to the room for each joule of electrical energy consumed ideally will be
$\dfrac{Q_{more}}{W} = \dfrac{Q_{more}}{Q_{more} – Q_{less}} = \dfrac{T_{more}}{T_{more} – T_{less}} = \dfrac{t_1 + 273}{t_1 – t_2}$
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A given sample of an ideal gas occupies a volume V at a pressure P and absolute temperature T. The mass of each molecule of the gas is m. Which of the following gives the density of the gas? |
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A body of mass m is attached to the lower end of a spring whose upper end is fixed. The spring has negligible mass. When the mass m is slightly pulled down and released, it oscillates with a time period of 3 s. When the mass m is increased by 1 kg, the time period of oscillations becomes 5 s. The value of m in kg is |
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The second overtone of an open organ pipe has the same frequency as the first overtone of a closed pipe L meter long. The length of the open pipe will be |
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Three sound waves of equal amplitudes have frequencies (n – 1), n, (n + 1). They superimpose to give beats. The number of beats produced per second will be |
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An electric dipole is placed at an angle of 30º with an electric field intensity 2 ×105 N / C. It experiences a torque equal to 4 N m. The charge on the dipole, if the dipole length is 2 cm, is |
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A parallel– plate capacitor of area A, plate separation d and capacitance C is filled with four dielectric materials having dielectric constant k1, k2, k3 and k4 as shown in the figure below. If a single dielectric material is to be used to have the same capacitance C in this capacitor, then its dielectric constant k is given by |
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The potential difference (VA – VB) between the points A and B in the given figure is |
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A filament bulb (500 W, 100 V) is to be used in a 230 V main suply. When a resistance R is connected in series, it works perfectly and the bulb consumes 500 W. The value of R is : |
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A long wire carrying a steady current is bent into a circular loop of one turn. The magnetic field at the centre of the loop is B. It is then bent into a circular coil of n turns. The magnetic field at the centre of this coil of n turns will be |
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A bar magnet is hung by a thin cotton thread in a uniform horizontal magnetic field and is in equilibrium state. The energy required to rotate it by 60º is W. Now the torque required to keep the magnet in this new position is |
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