Physics Test-19

Silver have a maximum number of electrons, so it is the best conductor of electricity because it contains a higher number of movable atoms (free electrons). Thus the valence shells and crystal structure of silver makes it the best conductor of electricity. Copper, silver, aluminum, gold, steel, and brass are common conductors of electricity.

As the temperature increases, the thermal conductivity of a gas increases.

Gases transfer heat by the collision of molecules. As the temperature increases, the kinetic energy of molecules of gases also increases and eventually collision between molecules also increases which increases the thermal conductivity of gases.

When the current flows in the same direction in the two parallel wires then both wires attract each other and if the current flows in the opposite direction in the two parallel wires then both wires repel each other.

Therefore, if the direction of flow of current is opposite in the two parallel wires separated by a small distance, then the wires will repel each other.

The dimension of kinetic energy is

\([E] = [ML^2T^{-2}]\)

Dimensions of mass, density, volume, velocity and acceleration are\([{m}]=[{M}]\)

\([{d}]=\left[{ML}^{-3}\right]\)

\([{V}]=\left[{L}^{3}\right]\)

\([{u}]=\left[{LT}^{-1}\right]\)

\([{a}]=\left[{LT}^{-2}\right]\)

A. Dimensions of the given options are:

The Electric Field for a uniformly distributed spherical charge is given by

Gauss' law states that the electric flux through any closed surface is equal to the total charge inside divided by \(\varepsilon _{0}\).

Charges are the source and sinks of the electric field. Since in a conducting material the electric field is everywhere zero, the divergence of \(E\) is zero, and by Gauss law, the charge density in the interior of the conductor must be zero.

Electromagnetic waves are the transverse waves.

Transverse Waves:

• Those waves whose direction of propagation and direction of disturbance is always perpendicular, are known as transverse waves.
• These waves produced in a medium that can sustain shearing strain.
• Example: Electromagnetic Waves, Ripples on the surface of water, Vibrations in a guitar string.

Concept:

The distance travelled by a body in \(n ^{\text {th }}\) second is given by:

\(S_{n}=\frac{u+a}{2}(2 n-1)\)

Where \(u\) is the initial velocity of the body, \(a\) is acceleration, and \(n\) is \(n ^{\text {th }}\) second.

Calculation:

Given that:

The ball is dropped from \(80 m\) height, so initial velocity \(( u )=0~ m / s\)

Acceleration is due to gravity \(( a )=10~ m / s ^{2}\)

and \(n=4\)

For \(n ^{\text {th }}\) second, \(S_{n}=\frac{u+a}{2}(2 n-1)\)

Distance travelled in \(4 ^{\text {th }}\) second \(\left( S _{4}\right)=0+\frac{10}{2}(2 \times 4-1)=35~ m\)

Therefore, the distance travelled by the ball in the fourth second will be \(35~ m\).

Power is defined as the rate of doing work or the rate of transfer of energy. If an agent does a Work (W) in Time (T), then power is given by:

\(Power\) \(=\frac{\text { Work }}{\text { Time }}\)

It is expressed in Watt (W).