#physics24feb2021
- An electromagnetic wave of frequency 5 GHz, is travelling in a medium whose relative electric permittivity and relative magnetic permeability both are 2. The correct answer is 15 n=√(μ_r ε_r)=2 v=cover n = 3×10⁸over 2 =15×10^(7 )m/s Hence X=15 the answer 1
- A common transistor radio set requires 12V (D.C.) for its operation. The D.C. source is constructed by using a transformer The correct answer is 440 N_pover N_s=V_pover V_s N_pover24=220over12 N_p=200×24over12 N_p=440 1
- An unpolarized light beam is incident on the polarizer of a polarization experiment and the intensity of light beam emerging The correct answer is 75 I₀cos²30°=100×(sqrt3over2)² =100×3over4 =75 1
- The coefficient of static friction between a wooden block of mass 0.5 kg and a vertical rough wall is 0.2. the correct answer is 25 N Given:: μ_s = 0.2 Solution:: m=0.5 kg g=10 m/s² We know that f_s= μ N To keep the block adhere to the wall here N... 1
- An audio signal υm = 20sin2π(1500t) amplitude modulates a carrier υc =80 sin 2π (100,000t). The value of percent modulation is ________. Correct answer is 25 v_m = 20 sin [100π t+πover4] :v_c = 80 sin [10⁴π t+πover6] we know that, modulation index = A_mover A_c from given equa... 1
- A resonance circuit having inductance and resistance 2 × 10–4 H and 6.28 Ω respectively oscillates at 10 MHz frequency. correct answer is 2000 R = 6.28 Ω f = 10 MHz L = 2 × 10⁻⁴ Henry We know that quality factor Q is given by ⇒ Q = X_L / R = ωL / R also, ω = 2... 1
- Each side of a box made of metal sheet in cubic shape is ‘a’ at room temperature ‘T’, the coefficient of linear expansion of the metal sheet is ‘α’. The correct Answer is C) 3a³αΔT ΔV = VγΔT ΔV = 3a³αΔT 2
- The work done by a gas molecule in an isolated system is given by, W = α.β2.e-x2 / αkT, where x is the displacement, k is the Boltzmann constant and T is the The correct option is c) MLT^(-2 ) we knnow that ,x² / α.k.T = dimensionless [x² / α.k.T ] = [M⁰L⁰T⁰] [α] = [L² / k.T] ⇒ [κ] = [M¹L²T⁻²K⁻¹]... 1
- The focal length f is related to the radius of curvature r of the spherical convex mirror by: The correct Answer is B) f = +½ r Explaination : So, r / 2 = f f = +½ r 1
- A current through a wire depends on time as i = α0t + βt2 where α0 = 20 A/s and β = 8 As-2. Find the charge crossed through a section of the wire in 15 s. Correct Answer is B) 11250 C Explaination :: we have , i = α₀t + βt² , α = 20 A/s and β = 8As⁻² ,t = 15 sec We know that , i= dqover dt⇒ ∫₀^... 1
- Statement-I: Two photons having equal linear momenta have equal wavelengths. Statement-II: If the wavelength of a photon is decreased, Correct option is d) Statement-I is true but Statement-II is false Energy of photon E = hc / λ = E ∝ 1 / λ Hence, energy of photon increases... 1
- Consider two satellites S1 and S2 with periods of revolution 1 hr and 8 hr respectively revolving around a planet in circular orbits. The correct answer is A) 8:1 we have formula , ω = 2over T given the, ratio of time period T₁over T₂=1over8 from formula, ω ∝ 1over T ω₁ ove... 1
- Four identical particles of equal masses 1 kg made to move along the circumference of a circle of radius 1 m under the action of their own mutual gravitational The correct option is A) space√( (1+2sqrt2)Gspace over2) explaination:: By resolving force F₂, we get F₁ + F₂ cos 45° + F₂ cos 45° = F_c F₁... 2
- In a transistor if increase in emitter current is 4 mA and corresponding increase in collector triangle I_E=4 \\ \\ \\ triangle I_c=3.5 \ \\α=triangle I_c over triangle I_E = 3.5over4=7over8 \\ \\ β= αover1-α=7over8over 1- 7over8=7 Hen... 1
- If two identical capacitor once connected in series (Ceq = C1) and once connected in parallel So Your answer is D c₁over c₂=1over4 1