Meter speed

[Gareth56]

Why is it that when I switch on my 60W desk lamp the wheel in my electric meter spins fairly slowly but when I switch on my 2.5kW electric kettle it spins around like nobody's business. Presumably the potential difference at the wall socket is always 220-240V so is it something to do with the resistance of the appliance?

[swansont]

I'm not sure I understand the question. Your 60W lamp draws 60 W. Your 2.5 kW kettle draws almost 42 times as much power, so you are using electrical energy at a much faster rate. That's why your meter spins faster.

 

Are you asking why the kettle draws more energy than the lamp?

[Gareth56]

Apologies for the vagueness. Let me try to elaborate. The voltage at the socket is the same [220-240V] irrespective of what the power rating of the appliance is that is connected to it. So if I plug in a 60W lamp the wheel on the meter spins relatively slowly and when I plug in a 2.5kW kettle is spins like hell. My question is why the difference in spin rates? Is the kettle drawing more current, i.e. electrons, from the socket than the lamp? If so why and how does the kettle "suck" more electrons from the wall socket?

 

Hope that helps.

[YT2095]

1 volt across 1 Ohm will draw 1 amp

1 volt across half an Ohm will draw 2 amps

and so on, but as you can see, in BOTH instances the voltage stays the same.

 

Volts x Amps = Watts

[thedarkshade]

I believe Tom gave a good enough reason. 2.5kW (2500W) is quiet greater than 60W, no matter what the voltage on the socket is. The voltage from the socket is transformed (decreased) until it's enough for the equipment to operate!

 

What about phone batteries? They have a voltage of 4.5V and are connected to a socket of 220V. Wouldn't this greater voltage burn the adapter that charged the phone? It doesn't because it reduces the voltage down to a point when it is enough to operate!

 

Volts x Amps = Watts

identical with:[math]P=UI[/math]

 

and the units work out because [math]P(=)UI=\frac{J}{C}\times \frac{C}{s}=\frac{J}{s}=W[/math]

[Gareth56]

1 volt across 1 Ohm will draw 1 amp

1 volt across half an Ohm will draw 2 amps

and so on, but as you can see, in BOTH instances the voltage stays the same.

 

Volts x Amps = Watts

 

So what's in the kettle that makes it "suck" more electrons from the wall socket than the lamp? Is it the resistance of the heating element? If so why does the resistance of the heating element of the kettle make the wheel of the meter spin faster than the filament of the lamp bulb?

 

By the way, is the resistance of the heating element in the kettle greater or less than the filament in the bulb of the lamp?

[YT2095]

it is indeed Resistance that makes the difference here.

 

the kettle will have a Lower resistance than the bulb.

 

 

identical with:[math]P=UI[/math]

 

and the units work out because [math]P(=)UI=\frac{J}{C}\times \frac{C}{s}=\frac{J}{s}=W[/math]

 

I think the best idea would be answer at the same level as the question.

I have a HNC in Electronics, and all that stuff even puts ME OFF!

 

best to keep things Simple a Real that can be related to easily

[Klaynos]

The relation between power and resistance can be found quite easily,

 

Start with

 

P=VI

 

And Ohms law

 

V=IR

 

And substitute the second into the first you get:

 

P=I²R

 

OR

 

P=V² / R

[thedarkshade]

The relation between power and resistance can be found quite easily,

 

Start with

 

P=VI

 

And Ohms law

 

V=IR

 

And substitute the second into the first you get:

 

P=I²R

 

OR

 

P=V² / R

Or another formula:

 

as: [math]A=UIt[/math] and [math]P=\frac{A}{t}[/math] then just put A in and you get

 

[math]P=\frac{A}{t}[/math]

 

[math]P=\frac{UIt}{t}[/math] and finally:

 

[math]P=UI[/math]

[J.C.MacSwell]

So what's in the kettle that makes it "suck" more electrons from the wall socket than the lamp? Is it the resistance of the heating element? If so why does the resistance of the heating element of the kettle make the wheel of the meter spin faster than the filament of the lamp bulb?

 

By the way, is the resistance of the heating element in the kettle greater or less than the filament in the bulb of the lamp?

 

The kettle resists less as YT said. This increases the flow of electricity.