Explanation

• An angle is dimensionless because it is defined as the ratio of arc length to radius, and both have the dimension of length.
• The SI unit of angle is the radian (rad).
• Other dimensionless quantities include strain, refractive index, and coefficient of friction.

Last verified on 28-10-2026

Explanation

• A moving coil galvanometer works on the principle that a current-carrying coil experiences torque when placed in a magnetic field.
• The torque causes the coil to rotate, and the attached pointer moves over a calibrated scale to indicate the electric current.
• A stronger current produces greater torque and a larger deflection, within the instrument’s normal operating range.

Last verified on 28-10-2026

Explanation

Torque on a current carrying coil in uniform magnetic field

tau = N I A B sinθ

where θ is the angle between the normal to the plane of coil and the magnetic field B.

When plane of coil is parallel to B, normal is perpendicular to B, θ = 90°, sinθ = 1, torque is maximum.

When plane of coil is perpendicular to B, normal is parallel to B, θ = 0°, sinθ = 0, torque is minimum (zero).

So torque is minimum when plane of coil is placed Perpendicular to the magnetic field.

Last verified on 28-10-2026

Explanation

• Charles' Law states that the volume of a fixed amount of gas is directly proportional to its absolute temperature when pressure remains constant.
• The formula is V1 / T1 = V2 / T2, where temperature is measured in Kelvin.
• When the temperature increases, the gas volume increases; when the temperature decreases, the volume decreases, provided the pressure remains constant.

Last verified on 28-10-2026

Explanation

• The capacitance of a parallel-plate capacitor is directly proportional to the plate area and inversely proportional to the distance between the plates.
• Doubling the plate area doubles the capacitance, while halving the distance doubles it again.
• Therefore, the new capacitance becomes 2 x 2 = 4 times the original capacitance.
• The formula is C = εA / d, where A is plate area, d is the separation, and ε is the permittivity of the material between the plates.

Last verified on 28-10-2026