dumb question on electricity

[loltolhurst]

if i have replaced a single 100w light bulb with a light that has 5 40w bulbs does that mean its using more energy and will cost me more? ie is it using 200w? If I fit a dimmer does that use less elec when you turn it down?

yes i have no idea about elec..

thanks!

[CommanderJameson]

loltolhurst said:

if i have replaced a single 100w light bulb with a light that has 5 40w bulbs does that mean its using more energy and will cost me more? ie is it using 200w? If I fit a dimmer does that use less elec when you turn it down?

Yes.
Yes.
Yes.

HTH!

[loltolhurst]

ta! im learning!

[Simpo Two]

I like that. Replacing a 100W light with a 200W light and running it at half power to save elctricity

[headcase]

Yup, half the calories so you can eat twice as much

[esselte]

CommanderJameson said:

loltolhurst said:

if i have replaced a single 100w light bulb with a light that has 5 40w bulbs does that mean its using more energy and will cost me more? ie is it using 200w? If I fit a dimmer does that use less elec when you turn it down?

Yes.
Yes.
Yes.

HTH!

The last bit's right so long as it's a modern SCR dimmer and not an older "rheostat" type...I think...

[Simpo Two]

esselte said:

The last bit's right so long as it's a modern SCR dimmer and not an older "rheostat" type...I think...

I thought that too - rheostats just dissipate the spare energy as heat. Electronic dimmers use a square wave I think, or something clever like that.

[esselte]

Simpo Two said:

esselte said:

The last bit's right so long as it's a modern SCR dimmer and not an older "rheostat" type...I think...

I thought that too - rheostats just dissipate the spare energy as heat. Electronic dimmers use a square wave I think, or something clever like that.

I think they turn the light on and off very quickly..obviously the longer it's off the dimmer the light....or something like that..

[CommanderJameson]

The Gory Details

The Website said:

Solid-state light dimmers work by varying the "duty cycle" (on/off time) of the full AC voltage that is applied to the lights being controlled. For example, if the voltage is applied for only half of each AC cycle, the light bulb will appear to be much less bright than when it get the full AC voltage, because it get's less power to heat the filament. Solid-state dimmers use the brightness knob setting to determine at what point in each voltage cycle to switch the light on and off.

Typical light dimmers are built using thyristors and the exact time when the thyristor is triggered relative to the zero crossings of the AC power is used to determine the power level. When the the thyristor is triggered it keeps conducting until the current passing though it goes to zero (exactly at the next zero crossing if the load is purely resistive, like light bulb). By changing the phase at which you trigger the triac you change the duty cycle and therefore the brightness of the light.

Here is an example of normal AC power you get from the receptacle (the picture should look like sine wave):

                  ...             ...             
                 .   .           .   .
                .     .         .     .
              ------------------------------------ 0V
                        .     .         .     .
                         .   .           .   .
                          ...             ...      

And here is what gets to the light bulb when the dimmer fires the triac on in the middle of AC phase:

                  ...             ...              
                  |  .            |  .
                  |   .           |   .
              ------------------------------------ 0V
                          |   .           |   .
                          |  .            |  .
                          ...             ...     

As you can see, by varying the turn-on point, the amount of power getting to the bulb is adjustable, and hence the light output can be controlled.

The advantage of thyristors over simple variable resistors is that they (ideally) dissipate very little power as they are either fully on or fully off. Typically thyristor causes voltage drop of 1-1.5 V when it passes the load current.

[loltolhurst]

so would one of these puppies use less elec?


http://www.screwfix.com/prods/47327/Electrical-Sup...



ta!

[garycat]

loltolhurst said:

so would one of these puppies use less elec?


http://www.screwfix.com/prods/47327/Electrical-Sup...



ta!

Yes.