Tangent Galvanometer and others

[coldfusion]

Why is it that in a tangent galvanometer the aluminium pointer is fixed perpendicular to the magnetic needle and not parallel? Anyways , why is the aluminium pointer used after all can't we just measure the current by the defletion of the needle ?


There is a statement that says "In a stationary wave all the particles in one loop are in the same phase while particles in the succeding loop are in opposite phase? " Can anyone explain ??


why is it that in deriving the expression for pressure exerted by a gas by the kinetic theory , we don't consider the gas molecule making collisions with any other molecule while colliding with the walls of the container back and forth ?


If a solid conducting mass is moved in a uniform magnetic field, with the field always perpendicular to the plane of the conductor then is emf induced considering there is no change of flux thru the conductor.

A Simple question to think about : If a hydrogen balloon is tied to the seat of a car moving in a circular path then what will be the direction of the balooon when windows are closed.
ie will it move 1) inwards toward the centre, 2) Outwards , 3) Remain vertical.

 

[Andrew Mason]

Why is it that in a tangent galvanometer the aluminium pointer is fixed perpendicular to the magnetic needle and not parallel? Anyways , why is the aluminium pointer used after all can't we just measure the current by the defletion of the needle ?

I expect that the aluminum needle provides the east/west reference so you can measure the deflection angle. The magnetic needle shows the deflection. But you have to measure the east/west component of its deflection to find the sine of the angle, the accuracy of which needed to measure small angles.

There is a statement that says "In a stationary wave all the particles in one loop are in the same phase while particles in the succeding loop are in opposite phase? " Can anyone explain ??

I think by phase they mean moving in the same direction (up or down). Phase usually refers to angle (ie. 0 => 2pi for one wavelength). Successive loops are always moving in opposite directions at any given time - ie. a phase difference of pi.

why is it that in deriving the expression for pressure exerted by a gas by the kinetic theory , we don't consider the gas molecule making collisions with any other molecule while colliding with the walls of the container back and forth ?

'We' do. But the collisions are elastic so the energy is simply passed on to other molecules. Ultimately, collisions between the molecules and the container wall produce the force on that wall.

If a solid conducting mass is moved in a uniform magnetic field, with the field always perpendicular to the plane of the conductor then is emf induced considering there is no change of flux thru the conductor.

The Lorentz force law: F = q\vec E + q\vec v \times \vec B applies. This force multiplied by a distance through which it acts determines the induced potential energy / unit charge or voltage (emf). The induced emf (E_{induced} = \vec v \times \vec B \times \vec{Distance}) becomes \vec v \times \vec B \times \vec L or vBL where L is the length of the conductor perpendicular to the direction of B and v is perpendicular to both L and v. There is no emf across the conductor width, so thickness of the conductor has no effect on the induced emf. However, no work is done, or energy consumed, by the voltage since no current flows in the conductor.

A Simple question to think about : If a hydrogen balloon is tied to the seat of a car moving in a circular path then what will be the direction of the balooon
ie will it move 1) inwards toward the centre, 2) Outwards , 3) Remain vertical.

But this may be a trick question if it asks about its direction of motion. The balloon has to continually move inward toward the centre in order to move in a circle. So although it leans outward relative to the car (so string tension can have a horizontal component to provide the centripetal force), it is continually changing direction (moving) toward the centre as well as tangentially.

AM

 

[wais]

The reason why the aluminium pointer in a tangent galvanometer is fixed perpendicular to the magnetic needle is because it allows for greater sensitivity and accuracy in measuring the current. When the pointer is perpendicular, it has a longer lever arm and can detect smaller deflections of the needle, resulting in more precise measurements.

The aluminium pointer is used in tangent galvanometers because it is a lightweight and non-magnetic material, which does not interfere with the magnetic field and the movement of the needle. It also allows for easy calibration and adjustment of the instrument.

In a stationary wave, the particles in one loop have the same amplitude and phase, while the particles in the succeeding loop have opposite phases. This is because the particles in the succeeding loop are traveling in the opposite direction, resulting in a phase difference of 180 degrees.

In the derivation of the pressure exerted by a gas using the kinetic theory, we do not consider collisions between gas molecules because they cancel out in all directions and do not contribute to the overall pressure exerted by the gas. The collisions with the walls of the container are the ones that result in a net force and contribute to the pressure.

If a solid conducting mass is moved in a uniform magnetic field with no change in flux, there will be no induced emf. This is because there is no change in the magnetic flux, which is necessary for inducing an emf.

When a hydrogen balloon is tied to the seat of a car moving in a circular path with closed windows, the balloon will move inwards towards the center. This is because the car is accelerating towards the center, causing a centripetal force that pushes the balloon inwards.