Physics - Online Test
If Vm and Im are peak voltage and current, Impedance Z in an AC circuit is
Impedance refers to the overall obstruction offered by a circuit containing different components to the passage of current. Also Z has unit same as resistance.
So, drawing an analogy with the ohm's law, we get the above relation
Streamlines are a family of curves that are instantaneously tangent to the velocity vector of the flow. These show the direction in which a massless fluid element will travel at any point in time
A streamline is one that drawn is tangential to the velocity vector at every point in the flow at a given instant and forms a powerful tool in understanding flows. This definition leads to the equation for streamlines.
where u,v, and w are the velocity components in x, y and z directions respectively as sketched.
If there are n number of molecules per unit volume and m is the mass of each , is the x-component of velocity, pressure can be written as
Pressure is due to collision of molecule with the wall of container.
Collision by moleculeto the wall of conntainer assumed to be perfectly elastic.
By the principle of conservation of momentum, the momentum imparted to the wall in the collision = 2mvx
the number of molecules hitting the wall in time =
n = no. of molecule per unit volume
A = Area of container
The total momentum transferred to the wall by these molecules in time =
Pressure P = F/A = rate of momentum transfer per unit area
all molecules in a gas do not have the same velocity; there is a distribution in velocities. The above equation therefore, stands for pressure due to the group of molecules with speed vx in the x-direction and n stands for the number density of that group of molecules. The total pressurer due to all groups
here, is the cyclotron frequency.
increase in volume per unit original volume per Kelvin rise in temperature is called coefficient of volume expansion,
Parallax Method of Measurement : Astronomers use an effect called parallax to measure distances to nearby stars. Parallax is the apparent displacement of an object because of a change in the observer's point of view.
To measure the distance D of a far away planet S by the parallax method, We observe it from two different positions (observatories) A and B on the Earth, separated by distance AB=b at the same time as shown in the given figure.
We measure the angle between the two directions along which the planet is viewed at these two points. The ∠ASB in the figure represented by symbol θ is called the parallax angle or parallactic angle.
As the planet is very far away, bD<<1 and therefore, θ is very small. Then we approximately take AB as an arc of length b of a circle with center at S and the distance D as the radius AS=BS so that AB=b=Dθ where θ is in radians.
