Dodgy wiring

[happysteve]

Or would it mean the bedroom light would only come on when the PIR triggered? She can see the outside light works, but doesn't realise there's a disco happening in her bedroom since she's outside triggering the PIR.

Bingo!

As Telectix says, some are more tolerant of voltage than others. If they're both tungsten/tungsten-halogen, then their brightness will depend on the voltage. If they're LEDs, then it won't (much) - they either work or they don't.

An interesting thing about incandescents: their resistance when off is a lot lower than when they're turned on, because as wires get hotter their resistance goes up. So a 100W GLS lamp will only have a resistance of about 530 ohms when it's got about 230V across it - below that, the resistance will be (I reckon, anyway) less.

 

[happysteve]

What's the first rule of steve?

The first rule of Steve is actually:

Write down what you know, in terms you understand.

E.g.:

Question, as written on the exam: "A load has power factor correction applied, so that the resulting impedance is 10 ohms when pf=1. The potential difference across the load is 230V a.c. What is the current through the load?"

What you write: R=10 (ohms), V=230 (volts); I = V/R

That way, you don't get muddled up by the way they phrase the question - they go on special courses on how to set questions this way... I think it's called the "sneaky b@5tard course"...

If that doesn't make things crystal clear, then you go to the second rule of Steve: If in doubt, draw it out.

 

[hightower]

The first rule of Steve is actually:

Write down what you know, in terms you understand.

E.g.:

Question, as written on the exam: "A load has power factor correction applied, so that the resulting impedance is 10 ohms when pf=1. The potential difference across the load is 230V a.c. What is the current through the load?"

What you write: R=10 (ohms), V=230 (volts); I = V/R

That way, you don't get muddled up by the way they phrase the question - they go on special courses on how to set questions this way... I think it's called the "sneaky b@5tard course"...

If that doesn't make things crystal clear, then you go to the second rule of Steve: If in doubt, draw it out.

I've even started doing that in class now - the lecturer might say "take this down. A voltage of 200v is applied across a resistance of 10ohms. Calculate the current."

Rather than write it all down my notes look like this:

V = 200V
R = 10Ohms
I = ?

 

[Dave OCD]

Old Dave got this right in post 2, but Happysteve and others explained it far more eloquently with the maths to back it up. :bulb2::laugh3:

 

[hightower]

Old Dave got this right in post 2, but Happysteve and others explained it far more eloquently with the maths to back it up. :bulb2::laugh3:

You did indeed dave, thanks has been sent your way in the shape of fake Internet points [emoji38]