Explanation

• According to Gauss's law, the net electric flux through a closed surface depends on the total charge enclosed within it.
• An electric dipole consists of equal and opposite charges, +q and -q. The net enclosed charge is zero.
• The formula is Flux = Q_enclosed / ε0 = 0 / ε0 = 0.

Last verified on 28-10-2026

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

• 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

Explanation

• The electric field lines of a positive point charge point outward, away from the charge.
• As we move farther away from the charge, the electric field strength decreases according to the inverse-square law.
• The electric field strength is given by E = kQ / r^2, where Q is the charge and r is the distance from it.

Last verified on 28-10-2026

Explanation

• Surface tension causes a liquid drop to minimize its surface area, making it tend toward a spherical shape.
• Surface tension arises due to the cohesive forces between liquid molecules at the surface.

Last verified on 28-10-2026

Explanation

• An ammeter measures the electric current flowing through a circuit.
• It is connected in series so that the same current flowing through the circuit also passes through the ammeter.
• An ammeter has very low resistance to minimize its effect on the current being measured.

Additional information:

• A voltmeter, in contrast, is connected in parallel to measure the potential difference across a component.

Last verified on 28-10-2026

Explanation

• Impulse J=F⋅Δt represents the change in momentum of an object.
• It is directly proportional to the force applied and the time duration of application.
• Impulse measures the effect of force over a time interval.

Last verified on 28-10-2026

Explanation

Scalar product = AB cosθ

Magnitude of vector product = AB sinθ

For equal magnitudes:

AB cosθ = AB sinθ

cosθ = sinθ

tanθ = 1

θ = 45°

So magnitude is equal at 45°.

Last verified on 28-10-2026