UN | MCQs

Explanation

Curie (Ci) is a unit that measures the rate of radioactive decay.

1 Curie = 3.7 × 10¹⁰ disintegrations per second.

Explanation

An alternative unit to kg ms⁻¹ is Ns (Newton-second).

This is because 1 N = 1 kg⋅m⋅s⁻², and multiplying by seconds gives Ns = kg⋅m⋅s⁻¹. 

Explanation

The correct equation representing Heisenberg's uncertainty principle is A) Δx. Δp ≥ ħ/2. 

This equation relates the uncertainty in position (Δx) to the uncertainty in momentum (Δp),

Where "ħ" is the reduced Planck constant. 

Explanation

Power = Work / Time = (Force × Distance) / Time

= (Mass × Acceleration × Distance) / Time

= [M] × [LT-2] × [L] / [T] = [ML2T-3].

Explanation

The kilowatt-hour (kWh) is a unit of energy commonly used to measure electricity consumption.

It represents the amount of energy used when a device with a power rating of 1 kilowatt operates for 1 hour. 

Additional information 

Energy/Work: Measured in joules (J).

Charge: Measured in coulombs (C).

Pressure: Measured in pascals (Pa).

Electric current: Measured in amperes (A).

Electric resistance: Measured in ohms (Ω).

Temperature: Measured in kelvin (K).

Torque: Measured in newton metres (N m).

Velocity: Measured in meters per second (m/s).

Acceleration: Measured in meters per second squared (m/s²).

Explanation

Using the Heisenberg Uncertainty Principle:

ΔE * Δt >= h/4π

where ΔE = h * Δv (energy uncertainty) and Δt = 10^(-8) s (lifetime)

h * Δv * 10^(-8) >= h/4π

Δv >= 1/(4π * 10^(-8))

≈ 8 x 10^6 Hz

Explanation

The unit of magnetic flux density is Wb m⁻² (weber per square meter).

It is commonly referred to as a tesla (T), which quantifies the strength of the magnetic field.

Explanation

An electron volt (eV) is a unit of energy.

It is defined as the amount of kinetic energy gained or lost by a single electron when it is accelerated through an electric potential difference of one volt.

Specifically:

1eV=1.602×10 −19 Joules

Thus, the electron volt is a convenient unit for measuring small amounts of energy, particularly in the fields of atomic and particle physics.

Explanation

The capacitance  𝐶 is defined as the charge  𝑄 stored per unit voltage  𝑉 

Mathematically, it's represented as:

𝐶 =𝑄/𝑉

So, 1 farad (F) is equal to 1 coulomb (C) per volt (V), but the equation doesn't imply that 

1C=1V.

Instead, it means that a capacitor has a capacitance of 1 farad if it can store 1 coulomb of charge when a voltage of 1 volt is applied across it.

Explanation

• An object moving along a circular path is experiencing a change in direction, which means it is constantly accelerating.
• According to Newton's first law of motion, an object in motion will remain in motion with a constant velocity unless acted upon by an external force.
• In the case of an object moving in a circular path, the force of centripetal acceleration is acting on the object, causing it to change direction and accelerate towards the center of the circle.
• Therefore, the object is not in equilibrium.