Physics
- The angle between the electric lines of force and the equipotential surface is : Answer: 4. 90° Work done in moving a charge along an equipotential surface is zero, so the field has no component along the surface. Hence e... 1
- A body of mass 60 g experiences a gravitational force of 3.0 N, when placed at a particular point. The magnitude of the gravitational field intensity at that point is : Answer: 3. 50 N/kg Gravitational field intensity is force per unit mass: E=F/m . m=60\ g=0.06\ kg⇒ E=3.0/0.06=50\ N/kg . Option (3). Using 6... 1
- The displacement-time graphs of two moving particles make angles of 30° and 45° with the x-axis as shown in the figure. The ratio of their respective velocity is : Answer: 1. 1 : √(3) On a displacement-time graph, velocity equals the slope, v=tanθ . v₁/v₂=tan30^°/tan45^°=1/sqrt3/1=1:sqrt3 . The 30 degre... 1
- The ratio of the distances travelled by a freely falling body in the 1^st, 2^nd, 3^rd and 4^th second : Answer: 4. 1 : 3 : 5 : 7 For a body falling from rest, the distance in the n th second is s_n=1/2g(2n-1) . So the distances in 1st, 2nd, 3rd... 1
- A shell of mass m is at rest initially. It explodes into three fragments having mass in the ratio 2 : 2 : 1. If the fragments having equal mass fly off along mutually perpendicular directions with speed v, the speed of the third (lighter) fragment is… Answer: 4. 2√(2) v The shell is at rest, so total momentum after explosion is zero. Masses are 2m/5,\ 2m/5 and m/5 . The two equal fragments... 1
- A long solenoid of radius 1 mm has 100 turns per mm. If 1 A current flows in the solenoid, the magnetic field strength at the centre of the solenoid is : Answer: 3. 12.56 × 10⁻² T Field at the centre of a long solenoid is B=μ₀ nI . n=100 turns/mm =10⁵ turns/m. B=4π×10⁻⁷×10⁵×1=0.1256\ T=12.56×1... 1
- Given below are two statements :Statement I : Biot-Savart's law gives us the expression for the magnetic field strength of an infinitesimal current element (Idl) of a current carrying conductor only.Statement II : Biot-Savart's law is analogous to Co… Answer: 4. Statement I is correct and Statement II is incorrect Statement I: Biot-Savart law gives the field due to a small current element... 1
- In a Young's double slit experiment, a student observes 8 fringes in a certain segment of screen when a monochromatic light of 600 nm wavelength is used. If the wavelength of light is changed to 400 nm, then the number of fringes he would observe in… Answer: 1. 12 Fringe width is β=λ D/d . For a fixed region of the screen, the number of fringes is N∝ 1/β∝ 1/λ . N₂=N₁λ₁/λ₂=8×600/400=12 Opt... 1
- A light ray falls on a glass surface of refractive index √(3), at an angle 60°. The angle between the refracted and reflected rays would be : Answer: 4. 90° Use Snell's law: sin60^°=sqrt3sin r⇒sin r=1/2⇒ r=30^° . The reflected ray makes 60^° with the normal, the refracted ray 30^°... 1
- Two pendulums of length 121 cm and 100 cm start vibrating in phase. At some instant, the two are at their mean position in the same phase. The minimum number of vibrations of the shorter pendulum after which the two are again in phase at the mean pos… Answer: 2. 11 Time period T∝sqrt l , so T₁₂₁:T₁₀₀=11:10 . They are next in phase when the shorter pendulum has made one more vibration than... 1
- The dimensions [MLT^-2A^-2] belong to the : Answer: 4. magnetic permeability Force has dimension MLT⁻² . Magnetic permeability appears in F=μ₀/4πI₁I₂ l/d , so μ₀ has dimensions of forc... 1
- Plane angle and solid angle have : Answer: 2. Units but no dimensions Plane angle is arc/radius (a ratio of lengths) and solid angle is area/radius squared, so both are dimens... 1
- If a soap bubble expands, the pressure inside the bubble : Answer: 2. decreases Excess pressure inside a soap bubble is Δ P=4S/r , so it is inversely proportional to the radius. When the bubble expan... 1
- A spherical ball is dropped in a long column of a highly viscous liquid. The curve in the graph shown, which represents the speed of the ball (v) as a function of time (t) is : Answer: 3. B A ball dropped in a viscous liquid starts with acceleration g . As speed grows, viscous drag rises, so the acceleration falls t... 1
- Two objects of mass 10 kg and 20 kg respectively are connected to the two ends of a rigid rod of length 10 m with negligible mass. The distance of the center of mass of the system from the 10 kg mass is : Answer: 3. 20/3 m Place the 10 kg mass at the origin and the 20 kg mass at 10 m. x_cm=10(0)+20(10)/10+20=200/30=20/3\ m The centre of mass l... 1
- The angular speed of a fly wheel moving with uniform angular acceleration changes from 1200 rpm to 3120 rpm in 16 seconds. The angular acceleration in rad/s^2 is : Answer: 3. 4π Convert rpm to rad/s using ω=2π N/60 . Δ N=3120-1200=1920 rpm, so Δω=2π×1920/60=64π\ rad/s . α=Δω/t=64π/16=4π\ rad/s² . Option... 1
- An ideal gas undergoes four different processes from the same initial state as shown in the figure below. Those processes are adiabatic, isothermal, isobaric and isochoric. The curve which represents the adiabatic process among 1, 2, 3 and 4 is : Answer: 3. 2 On a P-V diagram, all processes start from the same point. Curve 1 is vertical (constant volume, isochoric) and curve 4 is hori... 1
- An electric lift with a maximum load of 2000 kg (lift + passengers) is moving up with a constant speed of 1.5 ms^-1. The frictional force opposing the motion is 3000 N. The minimum power delivered by the motor to the lift in watts is : (g = 10 ms^-2) Answer: 4. 34500 At constant speed the motor force balances weight plus friction. F=mg+f=2000×10+3000=23000\ N P=Fv=23000×1.5=34500\ W Optio... 1
- Two resistors of resistance, 100 Ω and 200 Ω are connected in parallel in an electrical circuit. The ratio of the thermal energy developed in 100 Ω to that in 200 Ω in a given time is : Answer: 3. 2 : 1 In a parallel connection both resistors have the same voltage, so heat produced in a given time depends inversely on resist... 1
- As the temperature increases, the electrical resistance : Answer: 4. increases for conductors but decreases for semiconductors Resistance of a conductor rises with temperature, while that of a semic... 1
- When two monochromatic lights of frequency, and /2 are incident on a photoelectric metal, their stopping potential becomes V_s/2 and V_s respectively. The threshold frequency for this metal is : Answer: 1. 3/2ν Einstein's equation: eV_s=h(ν-ν₀) , so stopping potential is proportional to (ν-ν₀) . Taking the ratio of the two cases: V_s... 1
- The graph which shows the variation of the de Broglie wavelength (λ) of a particle and its associated momentum (p) is : Answer: 1. (graph) de Broglie wavelength is λ=h/p , so λ is inversely proportional to p . The graph of λ against p is therefore a rectangula... 1
- Match List - I with List - II :List - I (Electromagnetic waves): (a) AM radio waves (b) Microwaves (c) Infrared radiations (d) X-raysList - II (Wavelength): (i) 10^-10 m (ii) 10^2 m (iii) 10^-2 m (iv) 10^-4 mChoose the correct answer from the options… Answer: 1. (a) - (ii), (b) - (iii), (c) - (iv), (d) - (i) Recall typical wavelength ranges of the electromagnetic spectrum. AM radio waves:... 1
- Two hollow conducting spheres of radii R_1 and R_2 (R_1 >> R_2) have equal charges. The potential would be : Answer: 3. more on smaller sphere For a conducting sphere the potential is V=kQ/R , depending only on charge and radius, not on the material... 1