Physics
- For Young's double slit experiment, two statements are given below:Statement I : If screen is moved away from the plane of slits, angular separation of the fringes remains constant.Statement II : If the monochromatic source is replaced by another mon… Answer: 4. Statement I is true but Statement II is false. Fringe width β=λ D/d , so angular separation θ=β/D=λ/d . Statement I: θ does not d... 1
- The x-t graph of a particle performing simple harmonic motion is shown in the figure. The acceleration of the particle at t=2 s is : Answer: 1. -π²/16 mathrmm s⁻² From the graph, the amplitude is A=1 m and the particle is at the maximum at t=2 s, with a zero crossing at 4... 1
- The errors in the measurement which arise due to unpredictable fluctuations in temperature and voltage supply are : Answer: 1. Random errors Errors that arise from unpredictable, irregular fluctuations in conditions such as temperature or voltage supply ar... 1
- The venturi-meter works on : Answer: 3. Bernoulli's principle A venturi-meter measures the flow speed of a liquid in a pipe. In the narrow part the speed is higher and t... 1
- The amount of energy required to form a soap bubble of radius 2 cm from a soap solution is nearly : (surface tension of soap solution =0.03 N m^-1) Answer: 4. 3.01×10⁻⁴ J A soap bubble has two surfaces (inner and outer), so the energy needed equals surface tension times total area 2×4π r... 1
- The ratio of radius of gyration of a solid sphere of mass M and radius R about its own axis to the radius of gyration of the thin hollow sphere of same mass and radius about its axis is : Answer: Dropped in the official answer key: full marks to every candidate Radius of gyration is k=√(I/M) . Solid sphere about its axis: I=2/... 1
- A Carnot engine has an efficiency of 50% when its source is at a temperature 327^° C. The temperature of the sink is : Answer: 2. 27^° C Carnot efficiency: η=1-T₂/T₁ with temperatures in kelvin. T₁=327+273=600 K, η=0.5⇒ T₂=0.5×600=300 K = 27^° C. The answer i... 1
- The potential energy of a long spring when stretched by 2 cm is U. If the spring is stretched by 8 cm, potential energy stored in it will be : Answer: 1. 16U Spring energy U=1/2kx²∝ x² . Extension goes from 2 cm to 8 cm, a factor of 4, so energy goes up by 4²=16 . The new energy is... 1
- In hydrogen spectrum, the shortest wavelength in the Balmer series is λ. The shortest wavelength in the Bracket series is : Answer: 3. 4λ The shortest wavelength of a series comes from the transition from n=∞ to the series' lower level n₁ : dfrac1λ=R/n₁² , so λ∝ n... 1
- If the galvanometer G does not show any deflection in the circuit shown, the value of R is given by : Answer: 4. 100 Ω No deflection means no current in the galvanometer branch, so the potential drop across R equals the 2 V cell. Current in t... 1
- The work functions of Caesium (Cs), Potassium (K) and Sodium (Na) are 2.14 eV, 2.30 eV and 2.75 eV respectively. If incident electromagnetic radiation has an incident energy of 2.20 eV, which of these photosensitive surfaces may emit photoelectrons? Answer: 2. Cs only A surface emits photoelectrons only if the photon energy is at least its work function. Cs: 2.20 ≥ 2.14 eV, so it emits.... 1
- A 12 V, 60 W lamp is connected to the secondary of a step down transformer, whose primary is connected to ac mains of 220 V. Assuming the transformer to be ideal, what is the current in the primary winding? Answer: 2. 0.27 A An ideal transformer has no loss, so input power equals output power. Output power = 60 W, so V_pI_p = 60⇒ I_p=60/220≈ 0.2... 1
- In a plane electromagnetic wave travelling in free space, the electric field component oscillates sinusoidally at a frequency of 2.0×10^10 Hz and amplitude 48 V m^-1. Then the amplitude of oscillating magnetic field is : (Speed of light in free space… Answer: 4. 1.6×10⁻⁷ T In an electromagnetic wave in free space, E₀ = cB₀ . B₀=E₀/c=dfrac483×10⁸=1.6×10⁻⁷ T. The frequency is not needed. The... 1
- A full wave rectifier circuit consists of two p-n junction diodes, a centre-tapped transformer, capacitor and a load resistance. Which of these components remove the ac ripple from the rectified output? Answer: 4. Capacitor The rectifier output is pulsating dc. A capacitor connected across the load charges at the peaks and discharges in the... 1
- Given below are two statements:Statement I : Photovoltaic devices can convert optical radiation into electricity.Statement II : Zener diode is designed to operate under reverse bias in breakdown region.In the light of the above statements, choose the… Answer: 2. Both Statement I and Statement II are correct. Statement I is correct: photovoltaic devices (solar cells) convert optical radiati... 1
- An electric dipole is placed at an angle of 30^° with an electric field of intensity 2×10^5 N C^-1. It experiences a torque equal to 4 N m. Calculate the magnitude of charge on the dipole, if the dipole length is 2 cm. Answer: 1. 2 mC Torque on a dipole: τ = pEsinθ , with p=q· l . 4 = q(0.02)(2×10⁵)sin30^° = q× 2000 q = 2×10⁻³ C = 2 mC. 1
- If _S E· dS=0 over a surface, then : Answer: 2. the number of flux lines entering the surface must be equal to the number of flux lines leaving it. oint vec E· dvec S = q_enc/ε₀... 1
- The angular acceleration of a body, moving along the circumference of a circle, is : Answer: 1. along the axis of rotation Angular acceleration vecα = dvecω/dt is a vector along the axis of rotation, like vecω . For rotation... 1
- The temperature of a gas is -50^° C. To what temperature the gas should be heated so that the rms speed is increased by 3 times? Answer: 3. 3295^° C v_rms∝√(T) . The key reads \"increased by 3 times\" as the speed becoming v+3v=4v . T₁ = -50+273=223 K. v₂/v₁=4⇒ T₂=16T₁... 1
- A football player is moving southward and suddenly turns eastward with the same speed to avoid an opponent. The force that acts on the player while turning is : Answer: 4. along north-east Force is along the change in velocity, vec F∝ Δvec v=vec v_f-vec v_i . Initially the velocity is southward, -vha... 1
- The net magnetic flux through any closed surface is : Answer: 2. Zero Magnetic monopoles do not exist, so field lines always form closed loops: every line entering a closed surface also leaves i... 1
- Light travels a distance x in time t_1 in air and 10x in time t_2 in another denser medium. What is the critical angle for this medium? Answer: 1. sin⁻¹(10t₁/t₂) Refractive index n=c/v , and the critical angle satisfies sin C=1/n=v/c . Speed in air: c=x/t₁ . Speed in the medi... 1
- The ratio of frequencies of fundamental harmonic produced by an open pipe to that of closed pipe having the same length is : Answer: 3. 2 : 1 Fundamental frequency of an open pipe: f_o=v/2L . For a closed pipe: f_c=v/4L . f_o/f_c=4L/2L=2:1 . The answer is 2 : 1. 1
- A metal wire has mass (0.4±0.002) g, radius (0.3±0.001) mm and length (5±0.02) cm. The maximum possible percentage error in the measurement of density will nearly be: Answer: 4. 1.6% Density ρ=m/π r² l . The maximum fractional errors add, with the radius error counted twice because of r² . Δρ/ρ=Δ m/m+2Δ r/... 1