21.

Assertion: Air quickly leaking out of a balloon becomes cooler

Reason: The leaking air undergoes adiabatic expansion

• If both assertion and reason are true and reason is the correct explanation of assertion

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false

• If both assertion and reason are false

Assertion:  In pressure-temperature (P-T) phase diagram of water, the slope of the melting curve is found to be negative. 

Reason:  Ice contracts on melting to water

• If both assertion and reason are true and reason is the correct explanation of assertion

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false

• If both assertion and reason are false

Assertion: For higher temperatures the peak emission wavelength of a black body shifts to lower wavelengths. 

Reason:  Peak emission wavelengths of a blackbody is proportional to the fourth power of temperature.

• If both assertion and reason are true and reason is the correct explanation of assertion

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false

• If both assertion and reason are false

Assertion: For Reynold number R_e > 2000, the flow of fluid is turbulent. 

Reason: Inertial forces are dominant compared to the
viscous forces at such high Reynold numbers.

• If both assertion and reason are true and reason is the correct explanation of assertion

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false

• If both assertion and reason are false

A conducting ring of radius 1 meter is placed in a uniform magnetic field B of 0.01 tesla oscillating with frequency 100 Hz with its plane at right angle to B. What will be the induced electric field?

• $\mathrm{\pi }$ volts/m

• 2 volts/m

• 10 volts/m

• 62 volts/m

Two infinitely long parallel conducting plates having surface charge densities + σ and $-$σ  respectively, are separated by a small distance. The medium between the plates is vacuum. lf ε₀ is the dielectric permittivity of vacuum, then the electric field in the region between the plates is

• 0 volt/metre

• $\frac{\mathrm{\sigma }}{2{\mathrm{\epsilon }}_{\mathrm{o}}}$ volt/metre

• $\frac{\mathrm{\sigma }}{{\mathrm{\epsilon }}_{\mathrm{o}}}$ volt/metre

• $\frac{2\mathrm{\sigma }}{{\mathrm{\epsilon }}_{\mathrm{o}}}$ volt/metre

A 50 Hz a.c source of 20 volts is connected across  R and C as shown in figure. The volage across R  is 12 volt. The voltage across C is

• 8 V

• 16 V

• 10 V

• not possible to determine unless values of R and  C are given

In case of linearly polarised light, the magnitude of the electric field vector

• does not change with time

• varies periodically with time

• increases and decreases linearly with time

• is parallel to the direction of propagation

The circuit shown in the figure acts as

• tuned filter

• low pass filter

• high pass filter

• rectifier

For ensuring dissipation of same energy in all three resistors (R₁ , R₂ , R₃ ) connected as shown in figure, there values must be related as

• R₁ = R₂ = R₃ 

• R₂ = R₃ and R₁ = 4 R₂

• R₂ = R₃ and R₁ = (R₂/4)

• R₁ = R₂ + R₃