#units-dimensions-and-measurement
- The speed of light in a vacuum is 299,792,458 meters per second.
- A student measured the length of a rod and wrote it as 3.50 cm. Which instrument did he use to measure it? Measured length of rod = 3.50 cm That means least count of the measuring instrument should be 0.01 cm = 0.1 mm For vernier scale 1 main scal... 1
- Let E0 denote the dimensional formula of the permittivity of vacuum. If M = mass, L = length, T = time and A = electric current, then: Correct option is B From Coulomb's law we know, F = 1 over 4π in ₀q₁q₂ over r² therefore in ₀ = 1 over 4π q₁q₂ over Fr² Hence, [ in ₀ ] = [... 1
- Resistance of a given wire is obtained by measuring the current flowing in it and the voltage difference applied across it. If the percentage Correct option is A) 6% We know R = V over I thereforeΔ R over R = Δ V over V + Δ I over I Percentage error in R = Δ R over R × 100 = Δ V ov... 1
- The respective number of significant figures for the numbers 23.023, 0.0003 and 2.1 10–3 are Corret option is 1) 5,1,2 23.023 has 5 significant figures. 0.0003 has 1 significant figure. 2.1 × 10^(–3) has 2 significant figures. 1
- The dimension of magnetic field in M, L, T and C (coulomb) is given as Correct option is C) MT⁻¹C⁻¹ We know that, Lorentz force | overrightarrow F | = | qoverrightarrow v × overrightarrow B | therefore [B]=[F] o... 1
- Out of the following pair, which one does NOT have identical dimensions is A angular momentum and Planck's constant Correctt option is C) moment of inertia and moment of a force Moment of inertia, I = Mr² therefore [I] = [ML²] Moment of force, overrightarr... 1
- Which one of the following represents the correct dimensions of the coefficient of viscosity? option 1 is correct From stokes law, Viscous force F = 6π η rv ⇒ η = F over 6π rv therefore[η] = [MLT^(- 2)] over [L][LT^(- 1)] ⇒ [η] = [ML^... 1
- The physical quantities not having same dimensions are torque and work Correct option is 2) momentum and Planck's constant Momentum = mv = [MLT^(- 1)] Planck's constant, h = E over v=[ML²T^(- 2)] over [T^(- 1)]=... 1
- Dimensions of 1/u0E0 where symbols have their usual meaning, are Correct option is C ) [ L²T⁻² ] Explaination:: The velocity of light in vacuum is c = 1 over sqrt μ ₀ε ₀ therefore[1 over μ ₀ε ₀] = [c²] = [... 1