Candy's travels. London Nov 2021

That was a nightmare in London, particularly when the driver did not get back under the cables before the bus stopped. It could happen when he was steering past a parked or broken down vehicle.

 

I travel to my back yard and often. Doesn't cost me a cent........!

 

Do you have a transport museum in Brighton?
I am going to Brighton next month.

 

My clever professor. xxx

 

Trust you. lol
What about the casino?

 

Now that cost me plenty since I never win...............but at lest I see the girls....."looking" is for free.................lol

 

So do a photo thread. xxx

 

No cameras a lowed at the casino's............!

 

They have a Toy and Model Museum and a bird museum, but you have to be stuffed first

 

of course. I am a ditsy blonde with an E.

 

I think I went in the toy museum.
Birds?? mmmm

 

My problem is that I have the memory of a goldfish. Therefore I have to understand how everything works before I can start a job. Then I see problems in what exists already, so I have to redesign the whole lot.

For example, 240 is not how I remember the electricity voltage. To me, it is 415 (the phase voltage) divided by the square root of 3 (the number of phases)
The correct voltage is actually 239.6, but most people get lost by then.

As you can imagine, I don't get invited to too many parties. Especially those where people spend the evening discussing an imaginary character in Manchester played by an actor, having an affair with an equally imaginary character played by an actress.
I still remember the night that I was in the doghouse for laughing when one of Jane's friends was crying because the imaginary affair went wrong.

 

You always amuse me. X
Send me tips of what to visit in Greenwich.
I am there soon. X

 

No Candy darlin' but there is a transport museum not that far away in a little village called Amberley - just North of Arundel.

 

Candy darlin' travel to Greenwich from central London on the river - Westminster pier. On arrival at Greenwich you'll clearly see the Cutty Sark sailing ship and then not too far away from pier is the National Maritime Museum - you could spend all week in there !!!

 

I will x

 

RMS Value of AC | Derivation


In a DC system, the voltage and current are constant, therefore, there is no problem in specifying their magnitude. But in the case of an AC system, an alternating voltage varies from instant to instant and so poses a problem in specifying the magnitude.

So to express the AC quantities in an easy and understandable form, the concept of RMS value has been developed. They also can be expressed in terms of peak value or average value but these values don’t express the effectiveness of AC quantity.


Effective or RMS value of AC Current

The RMS value of AC current is equal to that amount of DC current which produces the same heating effect flowing through the same resistance for the same time.

The term RMS stands for the (square) root of the mean of the squares of instantaneous current values. The RMS value of AC current or voltage can be calculated from the following relation:

IRMS = 0.707 x peak value of current
VRMS = 0.707 x peak value of voltage



It is the actual value of an alternating quantity that tells us the energy transfer capability of an AC source. For example, if we say that 5A alternating current is flowing through a circuit, it means the RMS value of AC current flowing through the circuit is 5A. And it will produce the same amount of heat (energy) as will be produced by 5A DC current.

All the AC ammeters and voltmeters show the RMS values of alternating current and voltage respectively. All the electrical appliances are rated in the terms of RMS value. In India, the domestic single-phase AC supply is 230 V, 50 Hz. Here, 230 V is the RMS value of the supply voltage.

The RMS value of AC is always greater than the average value except for a rectangular wave when these are equal. Its value can never be negative.


Drive the Expression for RMS Value of AC

Let i = Im sinωt be the alternating current flowing through a resistance of R ohms for time t seconds and produces the same heat as produced by Ieff (a direct current).

The base of the half-cycle is divided into n equal parts as shown in Figure, so that each interval is of t/n seconds.



Let i1, i2, i3 ……….in be the mid-ordinates.

Then, heat produced in first interval = i12Rt/n joules
Second interval = i22Rt/n joules
Third interval = i32Rt/n joules
nth interval = in2Rt/n joules

Total heat produced in time t

= Rt[(i12 + i22 + i32 + ……+ in2)/n] …..(1)

Since Ieff is considered as the effective value of this current.
Then heat produced by this current in time t = Ieff2Rt …….(2)

By definition, equations (1) and (2) are equal. Therefore,

Ieff2Rt = Rt[(i12 + i22 + i32 + ……+ in2)/n]

Or Ieff2 = [(i12 + i22 + i32 + ……+ in2)/n]

Or Ieff = [(i12 + i22 + i32 + ……+ in2)/n]1/2

Or Ieff = IRMS = square root of the mean of the squares of the instantaneous current.

Now, by using the integral calculus the RMS or effective value of the alternating current over a time period can be calculated as follows:


Important Terms Related to RMS Value of AC

 

@Candy Gal you seem like a world traveler, is this correct? When I was younger I spent a lot of time traveling the globe, amazing experiences.

 

Yes kinda x