According to Kirchhoff's voltage law, the sum of the voltage drops must equal the source voltage. Here, 4V + 5V = 9V, which is correct.

Pressure is defined as force per unit area. The dimensions of force are ML^1T^-2, and area is L^2, thus pressure has dimensions ML^-1T^-2.

Ampere's Law states that the magnetic field around a closed loop is proportional to the electric current passing through the loop.

Gauss's law states that the electric flux through a closed surface is proportional to the charge enclosed within that surface.

Ohm's Law states that the current through a conductor between two points is directly proportional to the voltage across the two points, which can be expressed as V = IR.

The Biot-Savart Law describes the magnetic field generated by a steady current flowing through a conductor.

The first law of thermodynamics states that the total energy of an isolated system is constant, meaning energy can neither be created nor destroyed.

Surface tension is the energy required to increase the surface area of a liquid due to intermolecular forces.

Adding salt to water generally increases its viscosity.

According to F = ma, if the force is doubled, the acceleration also doubles.

The average kinetic energy of gas molecules is directly proportional to the absolute temperature. Therefore, increasing the temperature increases the average kinetic energy.

As the temperature of a gas increases, the average speed of gas molecules also increases due to the increase in kinetic energy.

Increasing the emf of the cell increases the balancing length, as it requires a longer length to balance the higher voltage.

The capacitance C of a capacitor is directly proportional to the dielectric constant k. If k is doubled, C also doubles.

Capacitance C = ε₀A/d; if d is doubled, C is halved.

Capacitance, C = ε₀ * A / d. If d is halved, C doubles.

The conductivity of a semiconductor increases with temperature due to the increased thermal energy that frees more charge carriers.

According to Ohm's Law, if resistance increases while voltage remains constant, the current decreases.

According to Ohm's Law, if voltage (V) is tripled and resistance (R) remains constant, the current (I) will also triple: I = V / R.

When the Wheatstone bridge is balanced, the current in the galvanometer becomes zero.

When the bridge is balanced, the current through the galvanometer becomes zero.

When the Wheatstone bridge is perfectly balanced, the current through the galvanometer is zero.

When the Wheatstone bridge is unbalanced, there is a non-zero potential difference across the galvanometer, causing current to flow through it.

When the Wheatstone bridge is balanced, the potential difference across the galvanometer is zero, resulting in zero current through it.

According to the ideal gas law, compressing a gas at constant temperature increases its density.

Replacing monochromatic light with white light results in a colored diffraction pattern due to the different wavelengths.

Increasing the distance between the slits decreases the fringe width, as fringe width is inversely proportional to the slit separation.

Increasing the distance to the screen results in an increase in fringe width in the diffraction pattern.

Decreasing the slit width increases the diffraction angle, causing the diffraction pattern to become wider.

The electric field is directly proportional to the charge. Tripling the charge will triple the electric field.